Overshorts

Part of speech: noun, verb

Definitions

1. Garments worn above regular shorts or underwear, providing an additional layer often for style or modesty
2. An outer layer of short pants designed to be worn on top of another pair of shorts or undergarments
3. Short pants intended as a covering layer over existing shorts or underwear for added coverage or fashion

Etymology: In its best-documented sense, "overshorts" is an accounting term for the amount by which a cash drawer or till comes up short of, or over, the expected total. It pairs with "overages" on the surplus side. The "short" here draws on the Old English "sceort," meaning "not long," which came to mean "lacking" or "deficient" in general. The clothing sense in your meaning is less well documented. The verb sense isn't one I can verify either.