某

Compound of 木 (나무 목, “tree”) + 甘 (달 감, “sweet”).

Originally meant plum tree.

Later borrowed (假借) for the abstract sense “a certain, someone, anonymous person”.

The botanical meaning was taken over by 梅 (매, plum tree).

某人 (모인) — someone, a certain person

某處 (모처) — a certain place

某日 (모일) — a certain day

某事 (모사) — a certain matter

김某씨 — Mr. Kim So-and-so (anonymous individual, name concealed)

Still widely used in classical Chinese and formal contexts, though in modern Korean journalism often replaced by A씨, B씨 for anonymity.