From Latin 'follis' (bellows, windbag), via Old French 'fol' — a fool was an empty bag of wind.
A person who acts unwisely; a jester.
From Old French 'fol' (mad person), from Latin 'follis' (bellows, leather bag, windbag). A fool is a bag of wind — empty and puffed up. Key roots: follis (Latin: "bellows, leather bag").