off one’s rocker

off (one's) rocker

Crazy; mentally unsound; extremely foolish. I'm going to go off my rocker if I have to hear that song one more time! I think Jane's grandmother is a little off her rocker these days. You must be off your rocker if you think that's a good idea!
See also: off, rocker

off one’s rocker

mod. silly; giddy; crazy. (see also rocker.) That silly dame is off her rocker.
See also: off, rocker