TgO Gen29:24 :וִיהַב לָבָן לַה יָת זִלפָה אַמתֵיה לְלֵאָה בְרַתֵיה לְאַמהוּ‏ : Laban gave his maid Zilpah to his daughter Leah in servitude
See the entire entry for ˀamhū, ˀamhūṯā n.f. service as a maid