phthisical (English) comes from Latin phthisicus, from Ancient Greek φθισικός, from Ancient Greek φθίσις, from Proto-Hellenic kʷʰtʰítis, from Proto-Indo-European dʰgʷʰítis, from Proto-Indo-European dʰgʷʰey- — to decline; to perish.
phthisical (English): phthisic