xeroderma (n.)

before vowels, xer-, word-forming element meaning "dry," from Greek xero-, combining form of xeros "dry, withered" (see xerasia).

"the true skin, the skin beneath the epidermis," 1706, from Modern Latin derma, from Greek derma (genitive dermatos) "(flayed) skin, leather," from PIE root *der- "to split, flay, peel," with derivatives referring to skin and leather.