köken: /d͡ʑauzu/ → /d͡ʑɔːzu/ → /d͡ʑoːzu/ From Middle Chinese compound 上手 (dzyangᴴ syuw^X, “to have the upper hand → to gain mastery, to master something”, literally “top hand”). This reading is likely a later innovation in Japanese after the initial borrowing. This uses the goon of jō for the first character, and the kan'yōon of zu for the second character.