馬鹿
ばか idiot; moron
Why it means this
馬 (horse) + 鹿 (deer) — ateji, possibly from Sanskrit moha ('folly'); a fool, an idiot; also 'ridiculously' (馬鹿正直; 馬鹿にする). A story ties it to a courtier who called a deer a horse to test the court's servility.
Breakdown
Each character links to its full entry — origin story, stroke order, and readings.