longies

noun[plural only]3

1. •
   (informal) knitted trousers for a baby or child

   • For longies, therefore, I cast on sufficiently for the waist, and work a piece of ribbing. — 1974
2. •
   (informal, old-fashioned) Full-length trousers for a young boy (as distinguished from knickerbockers).

   • Johnnie was in possession of the long trousers. He put them on. "How do I look in longies, Sam?" he laughed. — 1919
3. •
   (informal) long underwear.

   • I'm not going to change anything! Not even my underwear! And that's that. Get me my old red longies! — 1967