slip a cog

Idioms  

1. Also,. Lose one's ability to reason soundly or make correct judgments, as in She must have slipped a cog or she would never have gone out barefoot in December, or What's the matter with him? Has he slipped his gears? These slangy usages allude to a mechanical failure owing to the cog of a gear or a gear failing to mesh. The first dates from about 1930, the variant from the 1960s.

---

Example Sentences

On the second round, he seemed to slip a cog on the par-three fifth hole.

From Time Magazine Archive

I will try to answer your questions, but you know after a lapse of forty years, one’s memory may slip a cog.

From History of 'Billy the Kid' by Siringo, Chas. A.

"Yes, if they have had any warning or if our plans slip a cog anywhere we shall be repulsed to a certainty."

From Bucky O'Connor by Raine, William MacLeod

They will go on prospering; there is no further reason why he should bend a wire, slip a cog, or delay the hurrying wheels.

From Floyd Grandon's Honor by Douglas, Amanda Minnie

Perhaps this causes his romanticism to slip a cog, to run at times on a side-track, to become the servant of his religious partisanship.

From Lincoln; An Account of his Personal Life, Especially of its Springs of Action as Revealed and Deepened by the Ordeal of War by Stephenson, Nathaniel W. (Nathaniel Wright)