In the 18th and 19th centuries there were no visible pockets on women's clothing. So to carry things, British women wore a pair of detachable pockets that served a similar purpose to a handbag.
Dr Ariane Fennetaux is an Associate Professor at the Université de Paris, and she has co-written a book about detachable pockets, entitled The Pocket, A Hidden History of Women's Lives 1660-1900, which explores the social and cultural history of women's pockets.