off one's rocker

off one's rocker

1. (slang) Crazy; insane.

   He's off his rocker if he thinks he can tackle the whole thing alone.

   • 1960, P[elham] G[renville] Wodehouse, chapter VIII, in Jeeves in the Offing, London: Herbert Jenkins, OCLC 1227855:

     “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").