What is given to invite a response. A prompt shapes the answer as much as the one answering does.
Latin promptus (brought forth, ready at hand), past participle of promere (to bring forth, to produce): pro- (forth) + emere (to take); a prompt was first a readiness, only later the thing that invites the readiness.
What is given to invite a response, shaping the answer as much as the one answering does. Nothing answers a question that was never asked in some shape — the prompt is half of every reply it receives.