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
Alberta	[æl'bɜ:tə]
Stevenson	['sti:vnsn]
AslØG	-	Danish
Chandrakant	-	Indian, Marathi, Hindi
Nelly	NEL-ee	English
Otto	AW-to (German), AH-to (English), OT-to (Finnish)	German, Swedish, Norwegian, Danish, Dutch, English, Finnish, Ancient Germanic