'whodunit' originates from English, specifically the phrase 'who done it,' where 'who' refers to the person responsible and 'done it' refers to the act committed.

'who done it' transformed into the colloquial term 'whodunit' in the early 20th century, becoming a popular term for mystery novels.

Initially, it meant 'who did it,' but over time it evolved into its current meaning of 'a mystery or detective story.'