be as mad as a hatter

to be crazy

Usage notes: A long time ago, people who made hats used a substance that gave them an illness which made people think they were crazy.

Her brother's as mad as a hatter.

Name	Pronounced	Usage
Aldrin	['ɔ:ldrin]
Yorick	YAWR-ik (English), YAW-rik (Dutch), YO-rik (Dutch)	Literature, English, Dutch
Gayatri	-	Hinduism, Indian, Marathi, Hindi
Bingham	['biŋən]
Balthazar	-	Judeo-Christian Legend
Sollemnia	-	Late Roman