Undertrousers

This is composed of a short skirt and high gathered bodice, all in one, with full undertrousers in a separate piece.

Source: wiktionary

Roman wore a pair of loose undertrousers and slowly let himself into the water from the stern of the boat.

Source: wiktionary

Only undertrousers or drawers should be worn instead of petticoats. Indeed, petticoats are not to be included in a boy’s outfit after he is two years old.

Source: wiktionary

Two sets of clean room garment systems were used and tested: One clean room coverall having high filtration performance, and one set of cotton underwear and undertrousers, and one set of polyester underwear and undertrousers.

Source: wiktionary