In Scottish folklore, the fairy creature that can appear as a beautiful woman with goat’s legs is the glaistig.
The glaistig is a shape-shifting Scottish supernatural being, also called the Green Maiden or Green Lady. In one familiar form, she looks like an attractive woman, while her goat-like lower body is concealed beneath a long green dress. Other traditions portray her as a half-woman, half-goat creature or simply as a goat.
Her character varies sharply from story to story. Some tales make her a dangerous being who lures travelers or men with song and dance before attacking them. Other traditions describe a protective glaistig who guards cattle, deer, children, or herders. Milk was sometimes left as an offering to a benevolent spirit.
The glaistig is often confused with the kelpie, but a kelpie is primarily a Scottish water spirit, usually associated with a horse. The glaistig’s animal traits are goat-like, and her legends are tied more closely to forests, hills, cattle, and deer than to lakes and rivers.