early 15c., retreven, "find or discover again," originally in reference to dogs finding lost game, from retruev-, stem of Old French retreuver (Modern French retrouver) "find again, recover, meet again, recognize," from re- "again" (see re-) + trouver "to find," probably from Vulgar Latin *tropare "to compose," from Greek tropos "a turn, way, manner" (from PIE root *trep- "to turn").
Altered 16c. to retrive; modern form is from mid-17c. Specifically, of a dog, "to find and bring to hand game wounded or killed by a sportsman" is by 1856. The mental sense of "recall, recover by effort of memory" is from 1640s; computer sense of "obtain (stored information) again" is by 1962.