愚

Phono-semantic compound:

心 (마음 심, “heart”) — semantic, indicating emotions or mental state.

禺 (원숭이 우, also “long-tailed monkey”) — phonetic, providing the sound 우.

The combination depicts a heart/mind associated with lack of clarity, hence “foolishness.”

우매(愚昧) — ignorance, foolishness

우인(愚人) — a foolish person

우견(愚見) — “my humble opinion” (self-deprecating, polite)

우성(愚誠) — foolish sincerity, naïve devotion