Harry was staying at the Wynn resort, and the XS club was hosting an alcohol-fuelled party for Ryan Lochte's 28th birthday.
Harry was at the XS nightclub, part of the Wynn complex, where he had earlier been enjoying the club's 'Encore' Pool party.
And so far it is easy to follow his meaning: the XS are identical with some or all the Ys.
He got back yesterday—bought it off some feller up on th' XS.
So he said "Didn't you never correspond with a girl and put some of them XS down to the bottom of your letter?"
Item, payed for a brekefast lost at bolling by my Lady Mary's Grace, XS.
If the Qs or the XS were gone, it wouldn't so much matter; but there's hardly a word that hasn't at least one E in it.