at one's wit's end

at (one's) wit's end

In a state of distress that is reached when someone has no more patience. The baby's been crying for hours, and I'm at my wit's end! I'm already at my wit's end, so if this train gets delayed too, I'm going to scream.
See also: end

at one's wit's end

Also, at wits' end. Completely puzzled and perplexed, not knowing what to do. For example, I've tried every possible source without success, and now I'm at my wit's end. This idiom, which uses wit in the sense of "mental faculties," appeared in Piers Ploughman (c. 1377).
See also: end