polecat (n.)
early 14c., from cat (n.); the first element is perhaps Anglo-French pol, from Old French poule "fowl, hen" (see pullet (n.)); so called because it preys on poultry [Klein]. The other alternative is that the first element is from Old French pulent "stinking," for obvious reasons. Originally the European Putorius foetidus; also applied to related U.S. skunks since 1680s.