clean as a hound's tooth

(as) clean as a hound's tooth

1. Very clean; spotless. This house needs to be clean as a hound's tooth before Pop comes to visit.
2. Reputable and honest; free of wrongdoing. Oh, Donny is very trustworthy—his behavior has always been as clean as a hound's tooth.
See also: clean, tooth

*clean as a hound's tooth

 and *clean as a whistle 
1. Rur. Cliché very clean. (*Also: as ~.) After his mother scrubbed him thoroughly, the baby was as clean as a hound's tooth. The car was as clean as a whistle after the Girl Scouts washed it.
2. Rur. Cliché innocent and free from sin or wrong. (*Also: as ~.) Jane's record was clean as a whistle; she had never committed even the smallest infraction.
See also: clean, tooth

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.
See also: clean, tooth

clean as a hound's tooth

Completely blemish-free or honest. Another Southern expression; hounds' teeth are apparently cleaner than those of other species. Or perhaps just their canine teeth.
See also: clean, tooth