君主
くんしゅ · kunshu · JLPT N1 · noun
monarch
👑 君主 = 君 (sovereign lord) + 主 (master): the sovereign master who rules
Both characters carry the idea of lord. 君 names a sovereign and 主 names a master or owner, so the compound names the one who holds supreme power over a realm.
主 — flame/lamp on top of a stand 王
Originally a pictograph of a lamp with a flame on top of its stand, representing the lord or master of the household who tended the fire. The meaning extended from 'lamp/host' to 'master, owner, main, principal'. The character 炷 (wick) preserves the original 'lamp' sense.