phthisis (n.)

"disease of the lungs characterized by progressive disintegration of pulmonary tissue" (usually synonymous with pulmonary tuberculosis, consumption), c. 1300, tisik, pthisic, tphisike, etc., from Late Latin phthisis "consumption," from Greek phthisis "wasting, consumption; perishing, decay; waxing," from phthiein "to decay, waste away," from PIE root *dhgwhei- "to perish, die away" (source also of Sanskrit ksitih "destruction," ksinati "perishes"). The restored classical spelling is from early 16c.