What does the medical term thick skin mean?

Pachyderma: Thick skin, like that of a pachyderm (an elephant, rhinoceros, or hippopotamus). The adjective is pachydermatous. Pachyderma can occur in several medical conditions, such as chronic lymphedema. From the Greek pachydermos meaning "thick skin" from pachys meaning "thick" + derma meaning "skin."

What does Onychia mean?

Medical Definition of onychia

: inflammation of the matrix of a nail often leading to suppuration and loss of the nail.