A few cards short of a deck

Meaning

Slightly lacking intelligence or common sense.

Usage

Used jokingly about someone acting foolishly.

Origin & History

Origins and dates here are approximate summaries. Many idioms have disputed or unknown origins, and not every date has been checked against a historical dictionary, so treat specific dates and stories as a starting point rather than a citation.

Card game metaphor for missing elements.

Used since the mid-20th century in casual American slang.