ladies

Etymology

As a lavatory for women, via misspelling of ladies'. Compare gents.

noun

1. plural of lady
   He wet his thumb with saliva pressing on the tongue, ran it up and down faster over the letter 'I' of 'TOILET', the 'LADIES TOILET' was transformed into 'LADIES TO LET' in no time. 2014, C.S. Walter, Abandoned Bridges, pp. 105 f.
2. (obsolete) genitive of lady
   Vrge not my fathers anger (Eglamoure) / But thinke vpon my griefe (a Ladies griefe) / And on the iuſtice of my flying hence, / To keepe me from a moſt vnholy match, / Which heauen and fortune ſtill rewards with plagues. 1589–1593, William Shakespeare, “The Two Gentlemen of Verona”, in Mr. William Shakespeares Comedies, Histories, & Tragedies: Published According to the True Originall Copies, London: Printed by Isaac Iaggard, and Ed[ward] Blount, published 1623, act IV, scene iii, page 24
   And ſince not only a dead Fathers fame, / But more a Ladies honour muſt be touch’d, / Which nice as Ermines will not bear a Soil ; / Let all retire ; that you alone may hear / What ev’n in whiſpers I won’d tell your ear. 1690, John Dryden, Don Sebastian, King of Portugal: A Tragedy Acted at the Theatre Royal, London: Jo. Hindmarſh, act V, page 118

noun

1. (Britain, euphemistic) A ladies' room: a lavatory intended for use by women.
   Pardon me, I need to visit the ladies.