Whacko
/ˈwæk.oʊ/noun
An informal term for a person regarded as crazy or eccentric.
Did you know?‘Whacko’ is an expressive American slang formation tied to ‘whack’ in the sense of striking hard, showing how English can turn a violent sound-image into a label for mental instability.
Etymological Timeline
Late 19th Century
English
whack
“to strike sharply; a hard blow”
Early 20th Century
English
whacky / wacky
“slang for eccentric, odd, or crazy”
Mid 20th Century
English
whacko
“a crazy or eccentric person; also used as an adjective”
Modern English
English
whacko
“informal term for a mentally unstable, bizarre, or highly eccentric person”