mid-14c., prompten, "to incite to action, urge," from the adjective or from Latin promptus, past participle of promere "to bring forth," from pro "forward" (from PIE root *per- (1) "forward") + emere "to take" (from PIE root *em- "to take, distribute").
The meaning "coach (someone), assist (a learner or speaker) by suggesting something forgotten or imperfectly learned or known" is from early 15c.; specifically in the theatrical sense of "to assist a speaker with lines" by 1670s. Related: Prompted; prompting.
early 15c., "readiness" (in phrase in prompte), from Latin promptus (see prompt (v.)). Meaning "hint, information suggested, act of prompting" is from 1590s. The computer sense of "message given by a computer requiring or helping the user to respond" is by 1977.
early 15c., "ready, prepared (to do something), quick to act as occasion demands," from Old French prompt (13c.) and directly from Latin promptus "brought forth," hence "visible, apparent, evident, at hand," past-participle adjective from promere "to take or bring out or forth" (see prompt (v.)). Meaning "given or performed without delay" is from 1520s. Related: Promptly.