trolley

slang To be crazy and/or wacky. Usually used humorously. Don't listen to a word he says, he's off his trolley! You're off your trolley if you think that plan will work.

Fig. crazy; silly. (*Typically: be ~; go ~.) Sometimes, Bob, I think you're off your rocker. Good grief, John. You're off your nut.

Sl. to become a little crazy; to lose one's composure. I was afraid I would slip my trolley. He slipped his trolley and went totally bonkers.

to be crazy What are you doing eating chocolate and cheese again? You're off your trolley!

Also, off one's nut or rocker or trolley or chump . Crazy, out of one's mind, as in You're off your head if you think I'll pay your debts, or I think Jerry's gone off his nut over that car, or When she said we had to sleep in the barn we thought she was off her rocker, or The old man's been off his trolley for at least a year. The expression using head is colloquial and dates from the mid-1800s, nut has been slang for "head" since the mid-1800s; rocker, dating from the late 1800s, may allude to an elderly person falling from a rocking chair; trolley, also dating from the late 1800s, may be explained by George Ade's use of it in Artie (1896): "Any one that's got his head full of the girl proposition's liable to go off his trolley at the first curve." The last, chump, is also slang for "head" and was first recorded in 1859.

Also, off one's nut or trolley . See off one's head.

Out of one's mind; crazy.

Now you catch on. “Trolley” refers to the streetcars that predated buses and subways in major cities. To flounder around to the answer to a question or how to perform some sort of procedure and then to come up with the right answer was the equivalent of getting on a trolley that's on the right track (as in track of streetcar rails).