The Cotillion
The word cotillion was first used in 18th-century France and England to describe a group dance that is considered to be a forbearer of the square dance (à la the dancing in Pride and Prejudice). This specific dance came to be considered a good finale for any ball, which seems to translate well to its use today. Cotillion is typically a season of etiquette classes for middle-school aged children that ends with a final dinner-dance where they get to show off what they've learned.