undertrousers

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

1896 May 24, “Some of the New Bathing Suits”, in The Chattanooga Sunday Times, Chattanooga, Tenn., page 18

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.

1899 August 19, “Fashions for Children. There is Always Something New for Boys and Girls. Simplicity is the Keynote for Everything—Some Attractive and Serviceable School Frocks.”, in The Evening Star, number 14,500, Washington, D.C., page 8

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.

1988, Exploring World Partnerships in Technology: 9th International Symposium on Contamination Control: Proceedings, page 487

He lifted his skirts and there I saw his undertrousers. They were white and came to his knees. And his red socks also, held up with garters. It was so funny. He took from the shelf another pair of undertrousers and put them on.

1992, Mary Flanagan, Rose Reason, Harcourt Brace Jovanovich, page 304

“It’ll go away—keep your knickers on,” he added, shifting off the bed and casting around for his own undertrousers.[…]“I never once doubted that, Mi—Vielle,” he promised her, fastening his undertrousers in place.

2013, Angela Knight, Jennifer Ashley, Jean Johnson, Hanna Martine, Unbound, Berkley Sensation