Fang
late Old English (denoting booty or spoils), from Old Norse fang ‘capture, grasp’; compare with vang. A sense ‘trap, snare’ is recorded from the mid 16th century; both this and the original sense survive in Scots. The current sense (also mid 16th century) reflects the same notion of ‘something that catches and holds’.
wiktionary
From an abbreviation of fangtooth, from Middle English *fangtooth, *fengtooth, from Old English fængtōþ, fengtōþ(“canine tooth”, literally “snag-tooth, catch-tooth”). Cognate with German Fangzahn(“fang”, literally “catch-tooth”) and Dutch vangtand.
From Middle English fangen, from Old English fōn(“to take, grasp, seize, catch, capture, make prisoner, receive, accept, assume, undertake, meet with, encounter”), and Old Norse fanga(“to fetch, capture”), both from Proto-Germanic *fanhaną, *fangōną(“to catch, capture”), from Proto-Indo-European *peh₂ḱ-(“to attach”). Cognate with West Frisian fange(“to catch”), Dutch vangen(“to catch”), German fangen(“to catch”), Danish fange(“to catch”), Albanian peng(“to hinder, hold captive”), Sanskrit पाशयति(pāśáyati, “(s)he binds”).
From Middle English fang, feng(“a catching, capture, seizing”), from Old English fang, feng(“grip, embrace, grasp, grasping, capture, prey, booty, plunder”), from Proto-Germanic *fangą, *fangiz, *fanhiz(“catch, catching, seizure”), from *fanhaną(“to catch, capture”), from Proto-Indo-European *peh₂ḱ-(“to attach”). Cognate with Scots fang(“that which is taken, capture, catch, prey, booty”), Dutch vang(“a catch”), Low German fangst(“a catch”), German Fang(“a catch, capture, booty”), Swedish fång, fångst, Icelandic fang. Related also to Latin pangere(“to solidify, drive in”), Albanian mpij(“to benumb, stiffen”), Ancient Greek πήγνυμι(pḗgnumi, “to stiffen, firm up”), Sanskrit पाशयति(pāśáyati, “(s)he binds”).
etymonline
fang (n.)
Old English fang "prey, spoils, plunder, booty; a seizing or taking," from gefangen, strong past participle of fon "seize, take, capture," from Proto-Germanic *fāhanan (source also of Old Frisian fangia, Middle Dutch and Dutch vangen, Old Norse fanga, German fangen, Gothic fahan), from nasalized form of PIE root *pag- "to fasten" (source also of Latin pax "peace").
The sense of "canine tooth" (1550s) was not in Middle English and probably developed from Old English fengtoð, literally "catching- or grasping-tooth." Compare German Fangzahn. Transferred to the venom tooth of a serpent, etc., by 1800.
