From Late Latin apostolus, from Ancient Greek ἀπόστολος (apóstolos, “messenger, one sent forth”), from ἀποστέλλω (apostéllō, “I send off”), from ἀπό (apó, “from”) + στέλλω (stéllō, “I set”).
Practice speaking and memorizing "apostolo" and many other words and sentences in Italian.