with (one's) pants down

1. Trousers. Often used in the plural.

2. Underpants. Often used in the plural.

Word History: One would not expect a word for a modern article of clothing to come ultimately from the name of a 4th-century Roman Catholic saint, but that is the case with the word pants. It can be traced back to Pantaleon, the patron saint of Venice. He became so closely associated with the inhabitants of that city that the Venetians were popularly known as Pantaloni. Consequently, among the commedia dell'arte's stock characters the representative Venetian (a stereotypically wealthy but miserly merchant) was called Pantalone, or Pantalon in French. In the mid-17th century the French came to identify him with one particular style of trousers, a style which became known as pantaloons in English. Pantaloons was later applied to another style that came into fashion in the late 18th century, tight-fitting garments that had begun to replace knee breeches. After that pantaloons was used to refer to trousers in general. The abbreviation of pantaloons to pants met with some resistance at first; it was considered vulgar and, as Oliver Wendell Holmes put it, "a word not made for gentlemen, but 'gents.'" First found in the writings of Edgar Allan Poe in 1840, pants has replaced the "gentleman's word" in English and has lost all obvious connection to Saint Pantaleon.