c.1400, from Old French manumission "freedom, emancipation," and directly from Latin manumissionem (nominative manumissio) "freeing of a slave," noun of action from past participle stem of manumittere "to set free," from the phrase manu mittere "release from control," from manu, ablative of manus "power of a master," literally "hand" (see manual, adj.) + mittere "let go, release" (see mission).