go off (one's) dot(redirected from gone off his dot)
go off (one's) dot
To become crazy or mentally unsound; to become extremely foolish or foolhardy. I'm going to go off my dot if I have to hear that blasted song once more! I think Jane's grandmother has gone off her dot lately. You must have gone off your dot if you think that's a good idea!
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.