1520-30; < Middle Frenchapostille, noun derivative of apostiller to add marginal notes, derivative, with a-a-5, of Medieval Latinpostilla marginal note, perhaps from the phrase post illa (verba) after these (words), with illa construed as the Latin diminutive suffix
C16: from French apostille, from Old French apostiller to make marginal notes, from Medieval Latin postilla, probably from Latin post illa (verba) after those (words)