I have at least one suggestion.
Feet can be generous sources of pain, especially when used as primary transportation.
Saints need pain to transcend the flesh. They counter vanity effectively. The troubadour Raimon de Miraval mentions the pride of the peacock, and how it turns to shame when the bird catches sight of its hideous feet. They cannot be kept clean, either, especially when livestock wander the narrow city streets. It's not random.