toothyoudaoicibaDictYouDict[tooth 词源字典]
tooth: [OE] Etymologically, a tooth is an ‘eater’. Its ultimate source is the prehistoric Indo- European base *ed- ‘eat’, which also lies behind English eat and edible. From this was formed the noun *dont-, *dent- ‘tooth’, whose descendants include Latin dēns ‘tooth’ (source of English dentist, indent, trident [16], etc), Greek odón ‘tooth’, (source of English odontology [19]), Welsh dant ‘tooth’, and prehistoric Germanic *tanthuz. This evolved into German zahn, Dutch, Swedish, and Danish tand, and English tooth. A variant of *tanthuz may lie behind English tusk.
=> dentist, eat, edible, indent, odontology, trident, tusk[tooth etymology, tooth origin, 英语词源]
tooth (n.)youdaoicibaDictYouDict
Old English toð (plural teð), from Proto-Germanic *tan-thuz (cognates: Old Saxon, Danish, Swedish, Dutch tand, Old Norse tönn, Old Frisian toth, Old High German zand, German Zahn, Gothic tunþus), from PIE *dent- "tooth" (cognates: Sanskrit danta, Greek odontos, Latin dens, Lithuanian dantis, Old Irish 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. Tooth and nail as weapons is from 1530s. The tooth-fairy is attested from 1964.