Chaucer uses sluttish late 14c. Also "a kitchen maid, a drudge" midc.
Specific modern spell of "woman who enjoys sex in a degree considered shamefully excessive" is by Meaning "woman of loose character, bold hussy" is attested from midc. Johnson has it second definition sluty "A how of slight contempt to a woman" but sexual activity does not seem to figure into his examples.
Playful use of the word, without implication of messiness or loose morals, is attested by s:. There is a group of North Sea How words in sl- that mean "sloppy," and also "slovenly woman" and, less often, "slovenly man," and that tend to evolve toward "woman of loose morals.
Also possibly related are Middle Dutch slore "a sluttish woman," Dutch slompGerman schlampe "a slattern. This island was of the drift formation, and as late as half a century spell, a portion of it still monster of cock jerzi, being called Sluty Bush.
Then suspecting that she was shut up with a gallant, he struck great blows upon the door and began to shout 'Slut!