1620s, "set free from control," from Latin emancipatus, past participle of emancipare "put (a son) out of paternal authority, declare (someone) free, give up one's authority over," in Roman law, the freeing of a son or wife from the legal authority (patria potestas) of the pater familias, to make his or her own way in the world; from assimilated form of ex- "out, away" (see ex-) + mancipare "deliver, transfer or sell," from mancipum "ownership," from manus "hand" (from PIE root *man- (2) "hand") + capere "to take," from PIE root *kap- "to grasp." Related: Emancipated; emancipating.
Not used by the Romans in reference to the freeing of slaves, the verb for this being manumittere. The English word was adopted in the jargon of the cause of religious toleration (17c.), then anti-slavery (1776). Also used in reference to women who free themselves from conventional customs (1850).