Old English hyrian "pay for service, employ for wages, engage," from Proto-Germanic *hurjan (source also of Danish hyre, Old Frisian hera, Dutch huren, German heuern "to hire, rent"), of uncertain origin. Reflexively, "to agree to work for wages" from mid-13c. Related: Hired; hiring.
word-forming element in legal English (and in imitation of it), representing the Anglo-French -é ending of past participles used as nouns (compare -y (3)). As these sometimes were coupled with agent nouns in -or, the two suffixes came to be used as a pair to denote the initiator and the recipient of an action.
Not to be confused with the French -ée that is a feminine noun ending (as in fiancée), which is from Latin -ata.