This is where the word came from. Nobody uses "maiden" anymore, but nevertheless that is where "maid" comes from. People did at one time call an unmarried woman a maiden or maid, and a maiden or maid, as an unmarried young woman, was assumed to be a virgin: https://www.google.com/search?q=maiden+etymology&sca_esv=568251480&sxsrf=AM9HkKkqu5wRH8wp2Ye7yMROZNoSZnHUUQ%3A1695664453664&ei=RckRZb6OKJyuptQPgb-m6Ak&oq=maiden+et&gs_lp=Egxnd3Mtd2l6LXNlcnAiCW1haWRlbiBldCoCCAAyBRAAGIAEMgYQABgWGB4yBhAAGBYYHjIGEAAYFhgeMgYQABgWGB4yBhAAGBYYHjIGEAAYFhgeMgYQABgWGB4yBhAAGBYYHjIGEAAYFhgeSKwOUBNY1QFwAXgBkAEAmAFroAG9AaoBAzEuMbgBAcgBAPgBAcICChAAGEcY1gQYsAPCAgoQABiKBRiwAxhDwgIIEAAYigUYkQLCAgoQABiABBgUGIcCwgIFEC4YgATCAgsQLhiABBjHARivAeIDBBgAIEGIBgGQBgo&sclient=gws-wiz-serp