Cadaverous

Extremely thin and pale, resembling a dead body or corpse; gaunt and ghostly-looking.

From Latin 'cadaver' (dead body) + suffix '-ous' (full of). The Latin word likely derives from 'cadere' (to fall), since death involves the body falling into stillness. The adjective emerged in English in the 17th century to describe the haunting appearance of skeletal or emaciated people.