The story
Etymology from Wiktionary, CC BY-SA 4.0.
Today it means: A component of an interest rate floor, a derivative instrument that effectively prevents the interest payments on an otherwise variable-rate loan from falling below an agreed level (the "floor"). Each floorlet, analysable as a put option, covers one interest accrual period (such as three months); the whole interest rate floor is made up of a series of consecutive floorlets. Full definition →
Etymology from Wiktionary, CC BY-SA 4.0.