be off (one's) nut

slang To be crazy and/or wacky. Usually used humorously. Don't listen to a word he says, he's off his nut! You're off your nut if you think that plan will work.

Common Names:

Name	Pronounced	Usage
Sheelagh	SHEE-lə	English (Rare)
Haruki	hah-ṙoo-kee	Japanese
Alcides	-	Greek Mythology (Latinized), Portuguese, Spanish
FÓLki	-	Ancient Scandinavian
Kumbukani	kuw-mboo-KAH-nee	Southern African, Chewa
Bethan	BETH-an	Welsh