Visit the ladies' room
Euphemism for going to the lavatory.
Euphemisms are used whenever we need to talk about subjects that may cause embarrassment, which may include death, sex, poverty, disease and others, but it is with reference to lavatories that linguistic taboos really come into their own.
There has never been a polite word to describe 'the place for defecation and urination' and so for centuries we have invented words and phrases that refer to such a place without using those words. 'Lavatory' and 'toilet' are considered to be the grown up ways of so referring but even those are in fact euphemisms. A lavatorium is Latin for 'a place to wash clothes'. 'Toilet' originated in France, first as 'toile' then 'toilette', used to refer to washing and arranging one's hair, and came into English as the name for a piece of cloth used to cover clothes.
'Ladies' room' is one of the numerous euphemisms for lavatory: 'powder room', 'cloakroom', 'the smallest room in the house', 'facilities', 'WC', and so on (and on and on...). While it is true that 'ladies' room' is now a euphemism it wasn't originally coined as one. Public places such as theatres did provide private rooms for ladies to store their outdoor clothes and to titivate their appearance. 'Ladies' room' is a short form of 'ladies' cloak room', which was a literal description. Of course, it is now often further shortened to 'Ladies', in parallel with 'Gentlemen', now also shortened to 'Gents'.
'Ladies' Room' came into use in the Victorian era in Britain and here's an early example from an advert in the Burnley Gazette, June 1886:
Dining Room and Restaurant.
Also a first-class Ladies' Room.
Ladies and Gentlemen's lavatories, etc.
For the use of customers FREE.
The provision of a lavatory in a restaurant was clearly then novel enough to be worth publicising, in Burnley at least. Note the emphasis on 'free'. The 1880s was a time when the public would be expected to visit public toilets and 'spend a penny'.
We British are coy about sex but like to think that we are down to earth and Anglo Saxon about defecation. That's actually not the case. We like to identify with Shakespeare's bawdy and earthy humour but, in fact, the Bard was quite bashful about things lavatorial and avoided reference to defecation and urination. The nearest he got was referring to a lavatory as a 'bench-hole' in Anthony and Cleopatra. It is generally thought in the UK that the USA has cornered the market in toiletry diffidence and we point to 'restroom', 'john', 'little boys'/girls' room' and, most amusingly to our ears, 'comfort station'. Again, we have got that wrong. In Middle English 'comfort' was a synonym for 'easement' which is defined by the OED as (and I can't fall back on euphemism here) 'the relieving of the body by evacuation of excrement'. So 'comfort station' isn't evasive - it does exactly what it says on the tin (or as our US friends would say, 'can').