What comes back when something is asked. A response answers; it does not have to satisfy.
Latin responsum, from respondere (to answer, to pledge in return): re- (back) + spondere (to pledge, to promise); a response is a pledge sent back to meet a pledge sent first, and the root never required that it satisfy, only that it answer.
What comes back when something is asked. The root's pledging is the whole obligation: a response answers, and the root never promised that it would satisfy.