knickers 1. loosely fitting short breeches gathered in at the knee. 2. a bloomerlike undergarment worn by women

There is no third definition in Webster's. The first definition should sound familiar, because they're also known as golfing pants (and were part of the first baseball uniforms; you knew that was coming). The second is one of the least sexy articles of underclothing ever invented.

'knickers' is short for 'knickerbockers', who were the descendants of the original Dutch settlers of New York. I can only presume that the Dutch wore pants like that in the 1600s.