a sale of merchandise supposedly damaged by fire
a sale advertised in such a manner as to reasonably cause the public to believe that the sale will offer goods damaged by fire, smoke, water or other disaster
a sale held to give reason for the public to believe the sale will offer goods damaged or altered by fire, smoke, water or other means
A fire sale is the sale of goods at extremely low prices, typically when the seller faces bankruptcy or other impending distress. Perhaps originally based on a sale of goods at a heavy discount due to fire damage.
"Fire Sale" is the first episode of the Super Mario World cartoon.