county in Shaanxi province
郃 is a rare kanji that refers to a specific place name: a county in Shaanxi province. Its standalone meaning is limited to this geographical reference.
郃 combines 合 (to fit, join) with the city radical ⻏, likely representing a place name. The exact historical development is uncertain.
The left side 合 suggests joining or fitting, and the right side ⻏ indicates a city or place. Picture a county where different regions fit together like a puzzle.
For コウ, imagine a county official named Kou who oversees the joining of territories: Kou -> コウ.