off one's rocker
Definition from Wiktionary, the free dictionary
- (idiomatic) Crazy; insane.
- He's off his rocker if he thinks he can tackle the whole thing alone.
1960, P. G. Wodehouse, Jeeves in the Offing, chapter VIII:
- “Bertie! Your manner is strange.” “Your manner would be strange if you'd been sitting on the floor of Wilbert Cream's sleeping apartment with a chair round your neck, and Ma Cream had come in.” “Golly! Did she?” “In person.” “What did you say?” “I said I was looking for a mouse.” “Couldn't you think of anything better than that?” “No.” “And how did it all come out in the end?” “I melted away, leaving her plainly convinced that I was off my rocker.”
- A group is commonly qualified with a singular ("they're off their rocker") but sometimes also a plural ("they're off their rockers").