beautiful vault
n.— «Slot machines are sometimes called “beautiful vaults” in the industry because they bring in nearly three-quarters of the roughly $60 billion in gambling revenue that American casinos generate.» —“Slot Machines for the Young and Active” by Gary Rivlin New York Times Dec. 10, 2007. (source: Double-Tongued Dictionary)
Further reading
Brian from Lafayette, Indiana, wonders why chicken is abbreviated CHX in the restaurant industry. Using X as a substitute or shortener has a long history. Medieval scribes sometimes drew a line through the final stroke of an abbreviated word. This...
The expression to go chalk has to do with rankings in an athletic tournament and harks back to when seeded teams or players were listed on a chalkboard. To pick chalk means to choose one’s favorite competitor, and you can also speak of a chalk...