What does "tink, terry tink" mean in "I’ll mend them all with a tink, terry tink,"?
The original poem:
Have you any work for the tinker, brisk maids? Old brass, old pots, old kettles.
I'll mend 'em all with a tink terry tink and never hurt your metals.
First let me have but a touch of your ale, 'Twill steel me 'gainst cold weather.
Or tinkers freeze, or vintner's lees, or tobacco choose you whether.
But of your ale, your nappy ale, I would I had a firkin.
For I am old, and very very cold, and never a jerkin.
Tink could refer to the action of the tinker, or the sound made by the tinker at work. Apparently, the noise and the profession have been intertwined for some time; I found a gem of an excerpt from an 1882 book called Folk-etymology: A Dictionary of Verbal Corruptions Or Words Perverted in Form Or Meaning, by False Derivation Or Mistaken Analogy, which goes on to quote the first few lines of the 17th-century poem you cite (picture below).
Terry however, is a much tougher nut to crack. At first I wondered if it referred to the tinker polishing the kettle (as with a terry cloth) as he worked, but I don't like that theory at all. I checked the OED for terry; there were three listings, and only the first was around when the original poem was penned, and the second doesn't list terry being used as a verb:
terry, n.1 1563 ...A trodden path, sometimes a baulk or ridge of earth separating fields or allotments....
terry, n.2 and adj. 1784 ...The loop raised in pile-weaving (pile1) left uncut; also short for terry fabric, terry velvetB., etc., see B. In later use =...
terry, n.3 1907 ...A colloquial abbreviation of territorial, applied to members of the Territorial Army...
So my other theory (which I like better), is that maybe the word is a variant of tarry, meaning the tinker is taking his time as he mends the pot, probably in hopes that the "brisk maids" break down and eventually offer him something to drink. Moreover, the OED indicates that the word tarry had several variant spellings from the era when this poem was written, including tary, tarie, and tairrie:
Still, though, that's just a theory.
I don't believe terry is an adjective. "Tink, terry tink" is a written form of the cry of a tinker. Earlier in the book it reports the cry as "tara-tink" (page 81):
...I’ll mend them all with a tara-tink...
Tara is recorded as an exclamation1, so terry and tara could easily be the same word, slightly morphed by the fact that exclamations don't need consistent spelling or pronunciation.
Couple that with the facts that what you're reading is the written form of a cry (i.e. a simplistic advert - a call to let people know a tinker is available), and alliteration is a good way to get people's attention, I surmise that terry is just a word used to form a hook for the cry. It carries no meaning in the cry itself.
Since I believe that terry is a meaningless part of the cry, and that the phrase is a cry, tink itself is most likely to be the noun form referring to a tinker2.
"tara, int.1". OED Online. June 2012. Oxford University Press. http://oed.com/view/Entry/197759?rskey=DhQtKV&result=2&isAdvanced=false (accessed July 22, 2012).
"tink, n.2". OED Online. June 2012. Oxford University Press. http://oed.com/view/Entry/202254?rskey=eXNHOf&result=1&isAdvanced=false (accessed July 22, 2012).