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
Ekenedilichukwu	-	Western African, Igbo
Haf	-	Welsh
ÁSgeir	-	Icelandic
Cirillo	chee-REEL-lo	Italian
Emiliana	e-mee-LYAH-nah (Italian, Spanish)	Italian, Spanish, Portuguese
Lucilla	[lu:'si:lə]