From where did the term "sweet tooth" originate?

I don't think anyone knows for sure, but the expression dates at least from the 1600s. The earliest citations I can find in Google Books is:

"My sweet tooth long'd for a taste, and being very toothsdome, I did eat several"

- The English rogue: described, in the life of Meriton Latroon, a witty extravagant. Being a compleat history of the most eminent cheats of both sexes, 1665 http://books.google.co.uk/books?id=mGMXAAAAYAAJ&pg...

"The great Mutton is commonly course, and is not for a sweet Tooth"

- Nouvelle facile methode pour apprendre l'anglois, Guy Miege, 1698 http://books.google.co.uk/books?id=j_EU0u_0vo0C&pg...

"Is it because a liquorish Palate, or a sweet Tooth (as they call it) is not consistent with the Sanctity of his Character?"

- The lucubrations of Isaac Bickerstaff, esq, 1711, http://books.google.co.uk/books?id=lCEJAAAAQAAJ&pg...

When I was 16 I objected to the term- my son- which came from not my father but a complete stranger. My mate hates being called a Chav, I can't stand the term Middle aged, it sounds more like Middle ages ! Geriatric is another bone of contention ? What about Recycled teenager or Active Pensioner ? I think I prefer Senior Citizen, but there again that is only my own personal view. That is the trouble there are always those who want to pigeonhole and steriotype everyone, but everyone is an individual, at every age level and what seems to be either applicable to the age attained, the person might be either forward or backward to those years. A friend of mine is 41 but acts like a 80 year old, my mum when at 80 acted more like a teenager, so that leaves the question why catigorise in the first place? We are all part of the human race, as long as we don't come last who cares !!lol!!

Sweet Tooth Idiom

sweet tooth

"fondness for sugary stuff," late 14c., from sweet (adj.) + tooth in the sense of "taste, liking" (see toothsome under tooth).

tooth

O.E. toð (plural teð), from P.Gmc. *tanth, *tunth (cf. O.S., Dan., Swed., Du. tand, O.N. tönn, O.Fris. toth, O.H.G. zand, Ger. Zahn, Goth. tunþus), from PIE *dont-/*dent- "tooth" (cf. Skt. danta, Gk. odontos, L. dens, Lith. dantis, O.Ir. det, Welsh dent). Plural form teeth is an instance of i-mutation. Application to tooth-like parts of other objects (saws, combs, etc.) first recorded 1520s. Toothache is attested from late 14c. Toothbrush is first recorded 1650s; toothpaste first attested 1832; toothpick is from late 15c. Toothsome "pleasant to the taste" is c.1565; the fig. sense of "attractive" (1550s) is a bit older.

Maybe it comes from the toothache you get after eating to many sweets!