early 15c., "apply or devote (something to some purpose); expend or spend," from Old French emploiier (12c.) "make use of, apply; increase; entangle; devote," from Latin implicare "enfold, involve, be connected with, unite, associate," from assimilated form of in- (from PIE root *en "in") + plicare "to fold" (from PIE root *plek- "to plait").
Imply, which is the same word, retains more of the original sense. Sense of "hire, engage" first recorded in English 1580s, from meaning "involve in a particular purpose," which arose in Late Latin. Related: Employed; employing; employable.
1660s, "action of employing," from French emploi, from verb employer (see employ (v.)). From 1709 as "state of being employed."