A: Could you lend me 50 bucks?

B: What did you buy? This month has just begun.

A: My money gets spent so fast. It seems to vanish into thin air.

Note: This idiom is a cliche that means “to disappear without leaving a trace. Shakespeare came close to this phrase in “Othello,” in 1604: “Then put up your pipes in your bag... Go; vanish into air; away!” He also coined the term “thin air” (which has been widely used since the 17th century by many authors), but didn’t put the two together. The present usage first appeared in the 19th century. As we cannot see or touch air, it’s obvious that something having vanished into air is nowhere to be found.