Billy Day

Billy Day is a rhyming slang term, predominantly used in British English, meaning "pay day". It refers to the day on which an individual receives their salary or wages. The term plays on the similar sounds of "Billy" and "pay" and "Day" and "day." Its use is generally informal and more common in casual conversation. It is most often used when referring to one's own, or someone else's, upcoming pay day. The origin of the phrase is unknown but it is likely a 20th-century invention.