Paper promise

• Promissory note, of a sort
• Pot promise
• Lendee's note
• Indicator of shortness, for short
• Payment option that's not always accepted
• Gambler's marker
• Poker pot paper
• Brief note to a creditor
• Evidence of obligation

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
I O U \I O U\, IOU \I.O.U\([imac]" [=o]" [=u]"). [phonetic, from I owe you.] A paper having on it these letters, with a sum named, and duly signed; -- in use in England as an acknowledgment of a debt, and taken as evidence thereof, but not amounting to ...