@miyako19 Well, probably nobody's really sure. It's hard to accurately track the origins of slang terms since they spread the way they do. This is about the best you'll find for an origin of it getting popularized though I suppose. https://www.dictionary.com/e/slang/thot/I hate that stupid sexist word. Where did that come from anyway?
Although its exact origin remains unknown, thot appears to emerge out of the Chicago rap scene in late 2011.