lose one’s marbles
- verb to become deranged or feeble-minded, go crazy. Marbles, when referring to male faculties, usually refers to testicles, but in this case one’s wits or intelligence are in question. The origin of this phrase is uncertain, in spite of many attempts to clarify the choice of words (marbles have been seen as a synonym for the bearings which allow a machine to operate or as part of a catchphrase based on a story in which a monkey steals a boy’s marbles). What is undisputed is that the expression originated in the USA.
Idiom of “lose one’s marbles”
lose one’s wits or intelligence; become deranged