fightyoudaoicibaDictYouDict[fight 词源字典]
fight: [OE] The deadly earnestness of fighting seems to have had its etymological origins in the rather petty act of pulling someone’s hair. Fight, together with German fechten and Dutch vechten, goes back to a prehistoric Germanic *fekhtan, which appears to come from the same ultimate source as Latin pectere ‘comb’ and Greek péko ‘comb’.

The missing links in the apparently far-fetched semantic chain between ‘fighting’ and ‘combing’ are provided by such words as Spanish pelear ‘fight, quarrel’, a derivative of pelo ‘hair’, which originally meant ‘pull hair’; German raufen ‘pull out, pluck’, which when used reflexively means ‘fight’; and English tussle, which originally meant ‘pull roughly’, and may be related to tousle.
[fight etymology, fight origin, 英语词源]
fight (v.)youdaoicibaDictYouDict
Old English feohtan "to combat, contend with weapons, strive; attack; gain by fighting, win" (intransitive; class III strong verb; past tense feaht, past participle fohten), from Proto-Germanic *fehtan (cognates: Old High German fehtan, German fechten, Middle Dutch and Dutch vechten, Old Frisian fiuhta "to fight"), from PIE *pek- (2) "to pluck out" (wool or hair), apparently with a notion of "pulling roughly" (cognates: Greek pekein "to comb, shear," pekos "fleece, wool;" Persian pashm "wool, down," Latin pectere "to comb," Sanskrit paksman- "eyebrows, hair").

Spelling substitution of -gh- for a "hard H" sound was a Middle English scribal habit, especially before -t-. In some late Old English examples, the middle consonant was represented by a yogh. Among provincial early Modern English spellings, Wright lists faight, fate, fecht, feeght, feight, feit, feyght, feyt, feort, foight.

From c. 1200 as "offer resistance, struggle;" also "to quarrel, wrangle, create a disturbance." From late 14c. as "be in conflict." Transitive use from 1690s. To fight for "contest on behalf of" is from early 14c. To fight back "resist" is recorded from 1890. Well figt þat wel fligt ("he fights well that flies fast") was a Middle English proverb.
fight (n.)youdaoicibaDictYouDict
Old English feohte, gefeoht "a fight, combat, hostile encounter;" see fight (v.). Compare Old Frisian fiucht, Old Saxon fehta, Dutch gevecht, Old High German gifeht, German Gefecht. Meaning "power or inclination to fight" is from 1812.