A classic nursery rhyme from The Real Mother Goose
Lucy Locket lost her pocket,
Kitty Fisher found it;
Nothing in it, nothing in it,
But the binding 'round it.
Like a great many of Mother Goose's rhymes, the story of Lucy Locket was a reference to rather scandalous events. It was, in fact, about "the most detested man in England," the Earl of Sandwich, leaving his current mistress, Lucy Locket, in favor of the famous courtesan, Kitty Fisher.
The term "pocket" was used because, as her "keeper," to use the terminology of the day, Sandwich paid all living expenses of any woman he was... "protecting."
Kitty Fisher was of famously easy virtue, and enjoyed several affairs on the side during her time with Sandwich. There is record of one time Fisher entertained Lord Mountford while the Earl was away. He came home unexpectedly, though, and as Mountford heard him downstairs he begged Fisher to let him hide under her hoop skirt until he could safely escape. She refused, and Lord Mountford defenestrated himself, rather than confront the angry Earl.