Gilly

Part of speech: noun

Definitions

1. A slang term for an attractive woman or girl often implying flirtation or allure
2. A colloquial expression used to describe a lively social gathering, particularly among younger people
3. A playful name for a fish, particularly a gilly or gill, pertaining to aquatic life and their habitats

Etymology: English borrowed "gilly" from French, where the source form is written "Gilly." The capital letter in that spelling shows that the borrowed form was a name, and the word was then taken into English as a noun for a lively social gathering.