18th Century Pattens

Johnson’s Dictionary of the English Language defines a “patten” as

A ſhoe of wood with an iron ring, worn under the common ſhoe by women.

The V&A provides some additional context:

Pattens were worn to lift the shoe out of the dirt and damp. Being somewhat heavy and clumsy, they were mainly used by working-class or country women.

Several of the depictions of women wearing pattens (also linked below) are of maids who are using mops.