Why do eleven and twelve get unique words and not end in "-teen"?
In short, why is it not oneteen and twoteen, and we start at thirteen in English?
In another thread, I supposed that despite that fact that people have ten fingers, amounts of items leading up to and including twelve were more common because twelve is more easily divisible evenly by two, three, four, and six. Both English and German (which are related) switch to a -teen (-zehn auf Deutsch) ending after twelve. Based on that thread, so does Norwegian. Could this be the explanation?
Looking at other languages (Arabic, Japanese, even a related romance language of French), this doesn't seem to apply, and you'd think that if something so fundamental as divisibility were the explanation, we'd see a more universal distribution across them.
Actually, eleven and twelve also seem to be derived from 10+1 and 10+2. Let me quote from the classic book Number: The Language of Science by Tobias Dantzig (1930, republished with nice foreword by Barry Mazur):
Indeed, there is no mistaking the influence of our ten fingers on the “selection” of the base of our number system. In all Indo-European languages, as well as Semitic, Mongolian, and most primitive languages, the base of numeration is ten, i.e., there are independent number words up to ten, beyond which some compounding principle is used until 100 is reached. All these languages have independent words for 100 and 1000, and some languages for even higher decimal units. There are apparent exceptions, such as the English eleven and twelve, or the German elf and zwölf, but these have been traced to ein-lif and zwo-lif; lif being old German for ten.
And presumably this was inherited in other Germanic languages. (English, German and Norwegian all belong to the Germanic subfamily of Indo-European; French belongs to Italic.) Note that we can still discern a trace of "two" in "twelve".
That answers your question, but note that there are traces of other bases in our number words:
It is true that in addition to the decimal system, two other bases are reasonably widespread, but their character confirms to a remarkable degree the anthropomorphic nature of our counting scheme. These two other systems are the quinary, base 5, and the vigesimal, base 20. […]
Many languages still bear the traces of a quinary system, and it is reasonable to believe that some decimal systems passed through the quinary stage. Some philologists claim that even the Indo-European number languages are of a quinary origin. They point to the Greek word pempazein, to count by fives, and also to the unquestionably quinary character of the Roman numerals. However, there is no other evidence of this sort, and it is much more probable that our group of languages passed through a preliminary vigesimal stage. […]
While pure vigesimal systems are rare, there are numerous languages where the decimal and the vigesimal systems have merged. We have the English score, two-score, and three-score; the French vingt (20) and quatre-vingt (4 × 20). The old French used this form still more frequently; a hospital in Paris originally built for 300 blind veterans bears the quaint name of Quinze-Vingt (Fifteen-score); the name Onze-Vingt (Eleven-score) was given to a corps of police-sergeants comprising 220 men.
Also, we do have words like "dozen" (12) and "gross" (144) (any others?) for a few numbers not divisible by 5 (because highly divisible numbers are useful), but these words are sporadic and do not form the basis for any number-naming system in English as far as I know.
Edit: On further research, even though it's undisputed that eleven and twelve come from 1+10 and 2+10, the actual meaning of the lif part seems uncertain. The Online Etymology Dictionary confidently says:
c.1200, elleovene, from O.E. endleofan, lit. "one left" (over ten), from P.Gmc. *ainlif- (cf. O.S. elleban, O.Fris. andlova, Du. elf, O.H.G. einlif, Ger. elf, O.N. ellifu, Goth. ainlif), a compound of *ain "one" (see one) + PIE *leikw- "leave, remain" (cf. Gk. leipein "to leave behind;" see relinquish). Viking survivors who escaped an Anglo-Saxon victory were daroþa laf "the leavings of spears," while hamora laf "the leavings of hammers" was an O.E. kenning for "swords" (both from "The Battle of Brunanburgh"). Twelve reflects the same formation; outside Germanic the only instance of this formation is in Lithuanian, which uses it all the way to 19 (vienio-lika "eleven," dvy-lika "twelve," try-lika "thirteen," keturio-lika "fourteen," etc.)
But the OED says that "left" is just one theory:
Etymology: Common Teutonic: Old English ęndleofon corresponds to Old Frisian andlova, elleva, Old Saxon elleban (Middle Dutch elleven, Dutch elf), Old High German einlif (Middle High German eilf, German elf), Old Norse ellifu (Swedish ellifva, elfva, Danish elleve), Gothic ainlif < Old Germanic *ainlif- < *ain- (shortened < *aino-) [one] + -lif- of uncertain origin. Outside Teutonic the only analogous form is the Lithuanian vënó-lika, where -lika (answering in function to English -teen) is the terminal element of all the numerals from 11 to 19.
The Old English, Old Frisian, Old Saxon, and Old Norse forms represent a type *ainlifun, apparently assimilated to *tehun [ten]. The theory that the ending is a variant of Old Germanic *tehun, Aryan *dekm [ten], is now abandoned; some would derive it from the Aryan root *leiq or < *leip (both meaning to leave, to remain) so that eleven would mean ‘one left’ (after counting ten.)
An entirely different theory to ShreevatsaR's, which (I think) I read from Charles Seife's Zero: The Biography of a Dangerous Idea:
This is evidence of English having roots in a base-12 counting system. This was almost certainly based off counting using the joints of your fingers (four fingers, three joints), and using your thumb as a pointer to keep track of where you were.
As a computer scientist, I've trained myself to use a similar system using the tops of my fingers as well, giving base-16 counting on one hand.
I quote this helpful answer from Quora. In the interest of readability, I forgo quoting with > and edit the formatting lightly.
[TL;DR; Headnote] Eleven and twelve probably came from words meaning 'one-left' and 'two-left' -- left over, that is, after counting to ten. One explanation for the departure from the 13-19 pattern is that the Old Germanic ancestor languages of English could essentially only count up to ten, with hacks for numbers just over ten. The more computational system of the -teens later came to augment -- but did not replace -- the two ancient numerals.
Details: There are two sub-questions:
- What are the etymologies of the words eleven and twelve?
- Why don't these words fit the pattern of thirteen through nineteen?
[Answer to 1] A remarkably thorough answer to (1) appears at Why do eleven and twelve get unique words and not end in "-teen"? . (The part of the answer that begins "Edit: On further research..." is better than the main part of the answer.)
In brief, the answer is that eleven and twelve probably do fit a pattern -- a different one from the -teen words. Eleven is derived from Old Germanic *ainlif-, which is a combination of *ain-, meaning one, and -lif-, of uncertain origin [1]. A theory the Oxford English Dictionary ventures about the origin of -lif- is that it is cognate with Germanic words meaning "left" (in the sense of "remaining"), so that eleven is "one left" (that is, one remaining after counting ten), and twelve is, analogously, "two left". The theory that -lif- has something to do with ten is considered discredited by OED but not by all etymological dictionaries. There is not much etymological support, it seems, for the theory of a base-twelve origin of these words.
[Answer to 2] [...] 2 [, rephrased, becomes:] Why are 'eleven' and 'twelve' constructed according to a different pattern? 2 is a tantalizing question. I'll quote a speculation of Karl Menninger from the book Number Words and Number Symbols: A Cultural History of Numbers [2]. Menninger also subscribes to the "one left" and "two left" theory of eleven and twelve. He continues:
This is striking evidence that the Germanic number sequence at one time ran only as far as ten. Anything above that was "more". One and two more than ten were still counted, but anything beyond them was perhaps, as so often happens among primitive people, merely considered "many." Then along with the later clear conception of numbers, the subsequent computational number-word formations arose: 3'10 thir-teen, 4'10 four-teen, 5'10 fif-teen, and so on. (p. 84) [3]
Later, Menninger notes that "[n]umber words are among the words of a language that most strongly resist change" (p. 100). Thus it makes sense that the new, more logical/computational -teen words would augment but not replace the old "one left" and "two left" words. The durability of number words also supports the hypothesis that an extension of the "N left" system was not widespread in the ancestors of English, because if it had been, it probably wouldn't have been widely superseded by the -teen words.
Still, there is something a little odd about the theory that speakers of Old Germanic did not follow the pattern and start saying "three left", etc. -- that they used a hack to count slightly over ten, but stopped far short of using that idea to its full power. Such non-pattern-following would seem to correspond to a pretty early stage of intellectual development in the history of the Germanic tribes -- presumably before they came into regular contact with Romans, who knew how to count much higher. Incidentally, Lithuanian is the one Indo-European language known to actually have continued the pattern ("three left", "four left", all the way up to "nine left"); it has kept these words until today. Menninger (p. 84) says there is "no doubt" these number words were brought to the Lithuanians by migrating Germanic peoples; it is not clear whether the Germanic peoples brought only the start of the pattern (eleven and twelve) or the whole thing. If the latter is the case, then the observation at the end of the previous paragraph suggests that this was a fairly isolated Germanic innovation, one that did not take hold in many places -- otherwise, the -teen words would have had a hard time taking over.
Overall, our knowledge of the answer to question (2) is obviously much sketchier than of the answer to (1), but it is fun to speculate.
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[1] Paraphrasing the Oxford English Dictionary, under the entry eleven adj. and n.
[2]
[3] For another argument that the early Germanic tribes counted barely past ten, see pp. 85-86 of The Numeral Words by Melius De Villiers, http://books.google.com/books?id=KXFV-9w2VWUC&lpg=PA3&ots=My0Gl9DuI3&dq=eleven%20twelve%20germanic%20numerals&lr&pg=PA85#v=onepage&q=twelve&f=false . He also gives examples to suggest that in several other languages, just as in the West Germanic ones, the words for eleven and twelve are older and more primitive than those for 13-19.