Yes, EJ. You mentioned "undies" and someone else referred to said garments as "frillies". Here in England, "knickers" is an adequate description whenever (or if ever) it becomes necessary to mention them.

Come to think of it, as a child we had to wear thick green ones under a short tunic for gym. Mine got lost and one day a teacher wandered into our classroom looking for me because he had found a pair of green "unmentionables" bearing my name tape lurking in a corner of his classroom.

In the North East of England where I grew up, they were commonly referred to as "linings" as in the miner explaining (somewhat superfluously): Ah divvent wor white linings doon the pit.