What native word did "second" replace in English?

As far as I'm aware, the only cardinal or ordinal number in English of non–Anglo-Saxon/Germanic origin, under a million, is "second". I was wondering, how did it come about that this replaced a (presumably) native Anglo-Saxon ordinal for the number two?

I managed to dig up something that suggested that prior to early-Modern English, "other" was the ordinal for "second", but fell out of favour due to ambiguity. However, I was expecting a word more of the form "twoth" (which itself seems to exist on the odd occasion, but only as a neologism).

Examples from other West Germanic languages:

• Frisian: twadde
• Dutch: tweede
• German: zweite

(These are all cognate with the word "two", both in their own languages and more distantly in English of course.)

So it seems almost certain that in Old English (at least early Old English, but presumably extending until later), English had a cognate word. Does anyone have more information on this?

There seem to be three logical possibilities:

1. All the sources you have seen talking about the etymology of "second" and how it replaced the Old English cognate to other have neglected to mention an Old English word cognate to zweite.
2. Old English lost its word cognate to zweite.
3. You are mistaken in thinking that it is "almost certain" that zweite is inherited from common West Germanic.

I'm pretty sure the third is true.

There was no OE ordinal word built with the "two" root

Like the ordinals for ‘1’, those for the numerical value ‘2’ are all suppletive forms. There are two different lexemes which are employed for ‘second’.

OE ÆFTER ‘subsequent, following’ is a comparative formation containing a root which otherwise survives in the adverb OE EFT ‘afterwards, again’. In its weak inflected form æft(e)ra, it is sometimes used as an ordinal. In most instances, the implication ‘following’ cannot be completely interpreted away, and the strictly ordinal sense is implied by the contextual reading rather than by the primary lexical meaning of ÆFTER [...]. The use of ÆFTER with an exclusively ordinal function [...] is therefore rare.

[...] OÞER may be the default lexeme for the ordinal ‘second’. The use of this lexeme for ordinal number assignment is older, since it is attested in other Germanic and in some Indo-European languages, too. Like PDE other, the expression is used in a wide variety of senses and implications, such as ‘another’, ‘different’, etc., and instances where OÞER is used clearly and exclusively as an ordinal are again rare (Cardinal Numerals: Old English from a Cross-Linguistic Perspective, by Ferdinand von Mengden, pp. 122-123)

The "other" ordinal is attested across West Germanic languages

Paul (2007:232) points out that ander is the usual ordinal number for 'second' [in German] until the 16th century when it is replaced by zweit. (Quantifying Expressions in the History of German, by Dorian Roehrs, Christopher Sapp)

The trend mentioned in this quotation of zweit- taking over some of the functions of ander- in German over time is evidence that the "twoth" construction is an innovation in the West Germanic languages that have it, rather than something that existed in the common ancestor of German and English and then was lost in the latter.

It's unlikely that Old English lost an inherited "twoth" ordinal

The etymological argument against supposing the twoth-type ordinal goes back to common West Germanic is about the same as the one underlying the textual criticism concept of "lectio difficilior potior." It's more likely for an irregular ordinal such as "other" to be replaced by a regular ordinal like "twoth" than the reverse. The "twoth" word is, as you say, present in some modern West Germanic languages, but it is apparently not attested in Old English or older German texts. If you suppose it existed in common West Germanic, you have the problem of explaining why it was lost in Old English and Old High German (and how it was transmitted to modern German).

Words like twadde, tweede, zweite are not very strong evidence for reconstructing a "twoth" word in the common ancestor of West Germanic because they are all clearly composed of the "two" morpheme and the usual ordinal suffix "-th." It is not very surprising if it turns out this kind of regularized ordinal form is an innovation that replaced an inherited irregular ordinal form in several languages that are all geographically fairly close to one another, like German, Dutch and Frisian. And that seems to be what happened.

• Relevant sci.lang Google Groups discussion: Words for "ordinal 2" in Germanic languages.

All evidence I could find suggest that second replaced the original term , other, because of its ambiguousness:

Second:

• "next after first," c. 1300, from Old French

• Replaced native "other" in this sense because of the ambiguousness of the earlier word.

Other:

• Sense of "second" was detached from this word in English (which uses second, from Latin) and German (zweiter, from zwei "two") to avoid ambiguity. In Scandinavian, however, the second floor is still the "other" floor (Swedish andra, Danish anden). Also compare Old English oþergeara "next year."

(Etymonline)

Second:

• Partially displaced native other.

• From Middle English other, from Old English ōþer (“other, second”), from Proto-Germanic *anþeraz (“other, second”).

(Wiktionary)

From WWW

• Old English had a standard ending -(o)tha or -(o)the to create the ordinals (in modern English this has turned into -(e)th, as in fifth or twentieth) and it used them for the numbers from three onwards. However, it had no regularly formed ordinals for the numbers one and two (why that should be so is lost in prehistory) and it had to make do with whatever circumlocutions could be made to serve.

• To fill the blank for the number one, for example, Old English used various superlatives, including old versions of words that we now write as earliest and foremost. Our first, to start with in the forms fyrst or fyrest, appeared about the year 1000 but took over from the older terms a couple of hundred years later; it’s from Germanic predecessors that meant the foremost person in a society, a term we would now translate as prince. In Dutch and German it has evolved into vorst and Fürst in that sense.

• Expressing the idea of second posed similar problems but there wasn’t a word that could easily be adapted. Old English fell back on "other", which you will appreciate was horribly ambiguous.

• The situation was saved by the Norman Conquest of 1066, which brought the French word second into the language. This was from Latin secundus, the following or next in a series; it was based on sequi, to follow, from which we get sequel.