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.

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Example Sentences

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

From Time Magazine Archive

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)

And would nature allow it to choke up or slip a cog just because a little thing like a worm got tangled in its gearing?

From Quacks and Grafters by Unknown

"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

I know you can drive like—like you can work algebra, logyruthms, and never slip a cog.

From The Reclaimers by McCarter, Margaret Hill