little girls' room
Originally from the need to find public lavatories for children, possibly by analogy with the somewhat earlier-attested little boys' room, but already in broader euphemistic use by its first known appearance in John O'Hara's BUtterfield 8.
- (euphemistic, informal) Synonym of : a public lavatory intended for use by women.
- A room belonging to or used by little girls, particularly their bedroom.
- "little girl, n. and adj." in the Oxford English Dictionary (2014), Oxford: Oxford University Press.