Shoes for ladies in the late 18th and early 19th centuries were fairly daintily constructed, usually with fabric like silk or satin on the outside. They wouldn't hold up for a walk in the muddy lanes and byways so prevalent at the time. (Poorer women or those in the working classes, on the other hand, usually had sturdier shoes made of leather.) With so many of the gentry living in the countryside, some sort of overshoes had to be concocted to allow the women to, say, walk to church, and that is where pattens came in.
A patten was a sort of overshoe used for several centuries in England (and other places) to keep one's foot out of the muck. The person wearing a patten would fasten it over top their regular shoes, thereby elevating their feet from the ground and (hopefully) avoiding the mud. That said, in particularly muddy seasons, many of the women belonging to the gentry were essentially housebound because they could not avoid their feet sinking into (and possibly getting stuck in) the mud, to say nothing of the state of their skirts and petticoats.
Pattens were used to allow for surer footing, and so many dairy maids used them when milking, and housemaids used them when cleaning floors to avoid slipping. Pattens started to fall out of use once galoshes came along, but were still worn at least as late as WWI in rural areas in England.
If you're guessing that I know all of this because of my Jane research, you're correct. And yesterday, I completed a poem about pattens for my Jane book. But it had one stanza that truly doesn't fit for Jane, yet works as a nice poem about pattens, and so, without further ado, here 'tis:
Balanced on an iron perch,
Maids wear pattens mopping floors.
Please remove them while in church--
Wear in boggy lanes and moors.
If you'd like an interactive closeup of the patten above, by all means check out the online exhibit at the Bata Museum. And here are some of the prettier pattens for use in town:
Looking at today's rainy weather, I'm thinking I could probably use some pattens myself.