Old English ascian "ask, call for an answer; make a request," from earlier ahsian, from Proto-Germanic *aiskojanan (source also of Old Saxon escon, Old Frisian askia "request, demand, ask," Middle Dutch eiscen, Dutch eisen "to ask, demand," Old High German eiscon "to ask (a question)," German heischen "to ask, demand"), from PIE *ais- "to wish, desire" (source also of Sanskrit icchati "seeks, desires," Armenian aic "investigation," Old Church Slavonic iskati "to seek," Lithuanian ieškau, ieškoti "to seek").
Form in English influenced by a Scandinavian cognate (such as Danish æske; the Old English would have evolved by normal sound changes into ash, esh, which was a Midlands and southwestern England dialect form). Modern dialectal ax is as old as Old English acsian and was an accepted literary variant until c. 1600. Related: Asked; asking.
Old English also had fregnan/frignan which carried more directly the sense of "question, inquire," and is from PIE root *prek-, the common source of words for "ask" in most Indo-European languages (see pray). If you ask me "in my opinion" is attested from 1910.
prefix usually meaning "away, opposite, completely," from Old English for-, indicating loss or destruction, but in other cases completion, and used as well with intensive or pejorative force, from Proto-Germanic *fur "before, in" (source also of Old Norse for-, Swedish för-, Dutch ver-, Old High German fir-, German ver-); from PIE *pr-, from root *per- (1) "forward," hence "in front of, before, toward, near, against."
In verbs the prefix denotes (a) intensive or completive action or process, or (b) action that miscarries, turns out for the worse, results in failure, or produces adverse or opposite results. In many verbs the prefix exhibits both meanings, and the verbs frequently have secondary and figurative meanings or are synonymous with the simplex. [Middle English Compendium]
Probably originally in Germanic with a sense of "forward, forth," but it spun out complex sense developments in the historical languages. Disused as a word-forming element in Modern English. Ultimately from the same root as fore (adv.). From its use in participles it came to be an intensive prefix of adjectives in Middle English (for example Chaucer's forblak "exceedingly black"), but all these now seem to be obsolete.
From late Old English as "in favor of." For and fore differentiated gradually in Middle English. For alone as a conjunction, "because, since, for the reason that; in order that" is from late Old English, probably a shortening of common Old English phrases such as for þon þy "therefore," literally "for the (reason) that."