clean as a hound’s tooth

Spotlessly clean. This proverbial simile, current from about 1900, is as puzzling as one of its fifteenth-century antecedents, “clene as a byrdes ars.” The teeth of hounds are no cleaner than those of other carnivores, but therein may lie the source of the saying, that is, “clean” here may first have meant “sharp.” By the 1950s, however, when it was being applied to President Dwight D. Eisenhower’s administration, it meant clean in a more conventional figurative sense, that is, free of corruption.