
No, not the long-skirted woman. A butter worker is a piece of dairy equipment. But there’s churning and other stuff to do before you use a traditional, non-mechanical butter worker. Scroll down to find a video link if you want to see this right now.
The woman in the photograph has an old-fashioned dasher churn with lid and long handle. It makes butter when someone fills it with cream and then plunges the stick up, down and around. But the end result of churning is not good butter. To begin with, there are lots of little buttery fragments swimming in thin buttermilk. You need to strain these through cloth (like butter muslin) and let the buttermilk drain into a pail.
In the cloth you now have a lump of nearly-ready butter. It’s rinsed to flush out the remaining buttermilk, but it’s still damp and not pure butter in a smooth coherent piece. You may squeeze the lump between wooden boards to press out the last drops of milky water and encourage the butter to form into a whole. Next you “work” the butter, while mixing in salt evenly, with wooden butter hands on a board, or with the back of a wooden ladle or a presser in a bowl.
A new kind of butter worker

A different kind of butter worker emerged in the first part of the 19th century. The big picture shows one of the new kind in the kitchen of a German-American Wisconsin farmhouse. It seems like a good design: tilted to help liquid drain away through the holes, simple to make with home carpentry skills, and easy to operate. Moving the rod from side to side over the butter will press it and “work” it into good shape.

The simplest of the “modern” butter workers are generally only slightly more complicated than using a rolling pin on a wooden table. In the course of the 1800s more sophisticated combinations of roller and board were introduced. Rollers cranked by a handle, using metal fixings, lightened the work without being too complicated or expensive. People started to patent a variety of designs.

In the picture the kitchen looks crowded with the butter worker and of course it is not a likely place for it to have been originally. You always need to do dairy work in a cool place even if you don’t have a dedicated dairy building. In a traditional kitchen the hot stove or hearth makes the room unsuitable for making butter or for doing any other work with milk or cream.
Butter making video
If you want to see the whole process, watch this video.
First you see the simplest way of making butter. A dairymaid skims cream off flat dishes of milk, churns, drains, rinses and works the butter before shaping a block with wooden “Scotch” hands aka butter pats. (She makes it look easy. Practice makes perfect.) Then the film shows mechanised churning with an end-over-end churn of a late 19th century or early 20th century type.
A butter worker from the 1840s, and one from the 1890s

Among the implements particularly worthy of notice, was a butter-worker, presented by Amherst Hawes, from the farm of Col. J. W. Lincoln, Worcester [Mass.]. It was a kind of brake. A marble slab placed on a table, with a slight declivity to let the buttermilk run off, formed the place for working the butter. A fluted roller, to which was attached a handle three or four feet long, fastened at the lower end to a swivel, constituted the power for working the butter, which was done by passing the roller backwards and forwards over it, applying as much pressure by means of the hand, as is required.
From: The Cultivator, A Monthly Journal to Agriculture, Horticulture, Floriculture and to Domestic and Rural Economy, Albany NY, 1844
Photos
Photographers credited in captions. Links to originals here: Woman with churn and Kitchen picture. Also see more picture info here.