Rain slippers were a type of footwear made by the Ferengi for use in wet areas, such as on Ferenginar itself.
In 2374, Quark was told by the nephew of the cousin of the stepsister of a friend of the secretary of the chief accountant of the Balancar Agricultural Consortium that the accountant had bought a pair of rain slippers, which led Quark to deduce that a reported drought on Balancar was fictitious. Quark's deduction proved correct, and it transpired that the Consortium had faked the drought so that they could stockpile syrup of squill in order to drive the price up. (DS9: "The Magnificent Ferengi")