The story
A clipped form of gentlemen. As a room, via misspelling of gents', a clipped form of gentlemen's room.
Etymology from Wiktionary, CC BY-SA 4.0.
gents
Today it means: A men's room: a lavatory intended for use by men. Full definition →
Today it means: A men's room: a lavatory intended for use by men. Full definition →
A clipped form of gentlemen. As a room, via misspelling of gents', a clipped form of gentlemen's room.
Etymology from Wiktionary, CC BY-SA 4.0.