would: [OE] Would goes back to wold-, the Old English past tense of will. Its vowel is inherited from the Indo-European variant *wol- (as in German wollen ‘will, want’), rather than the *wel- that produced the English present form will. Its use as an auxiliary to form the conditional dates back to the Old English period. => will[would etymology, would origin, 英语词源]
Old English wolde, past tense and past subjunctive of willan "to will" (see will (v.)). Would-be (adj.) "wishing to be, vainly pretending" is first recorded c. 1300.