everyoudaoicibaDictYouDict[ever 词源字典]
ever: [OE] For such a common and longestablished word, the origins of ever are surprisingly obscure. It has no relatives in other Germanic languages, so it must be a purely English creation. Its first element probably comes from Germanic *aiwō (which is also represented in English aye ‘ever’ [12] and either, and is related to Latin aevum ‘age’, source of English eternal).

The second element is a puzzle, though. Candidates that have been put forward include Old English feorh ‘life’ (thus, ‘ever in life’) and Old English byre ‘occasion’ (giving the underlying sense ‘on any occasion’). Never was formed in the Old English period with the negative particle ne.
=> aye, either, eternal[ever etymology, ever origin, 英语词源]
ever (adv.)youdaoicibaDictYouDict
Old English æfre "ever, at any time, always;" of uncertain origin, no cognates in any other Germanic language; perhaps a contraction of a in feore, literally "ever in life" (the expression a to fore is common in Old English writings). First element is almost certainly related to Old English a "always, ever," from Proto-Germanic *aiwo, from PIE *aiw- "vital force, life, long life, eternity" (see eon). Liberman suggests second element is comparative adjectival suffix -re.

Sometimes contracted to e'er in dialect and poetry. Ever began to be used in late Old English as a way to generalize or intensify when, what, where, etc. The sense evolution was from "at any time at all, in any way" to "at any particular time; at some time or another; under any circumstances." Ever so "to whatever extent" is recorded by 1680s. Expression did you ever? (implying "see/do/hear of such a thing") attested by 1840.