A slattern is a woman thought dirty and untidy, in old use. Called her a slattern, an idle slattern.
It is archaic and insulting, and it belongs to a set of words applied to women and never to men for the same behaviour — which is the interesting thing about it now. It appears in historical fiction and nowhere else. It comes from a dialect verb meaning to slop or spill.
1nounslatternA woman thought dirty and untidy, in old use.
“In the old novel, the landlady calls the maid a lazy slattern for leaving the kitchen dirty.”
slattern is an old insult.
From the dialect verb slatter, to slop or spill, recorded from the seventeenth century.
Dating from the 17th century; related to slattering (“slovenly”), from the dialectal verb slatter (“to slop, to spill”).
Etymology from Wiktionary, CC BY-SA