whyyoudaoicibaDictYouDict[why 词源字典]
why: [OE] Why goes back to Indo-European *qwei, the locative case of the interrogative base *qwo- (source of English what and who). This passed into prehistoric Germanic as *khwī, which has since died out in all the Germanic languages apart from Danish (hvi) and English (why).
[why etymology, why origin, 英语词源]
why (adv.)youdaoicibaDictYouDict
Old English hwi, instrumental case (indicating for what purpose or by what means) of hwæt (see what), from Proto-Germanic adverb *hwi (cognates: Old Saxon hwi, Old Norse hvi), from PIE *kwi- (source of Greek pei "where"), locative of *kwo- "who" (see who). As an interjection of surprise or emphasis, recorded from 1510s. As a noun, "cause, reason" from c. 1300.