From Proto-Italic *(k)sitis, from Proto-Indo-European *dʰgʷʰítis (“perishing, destruction, decrease”), from *dʰgʷʰey- (“to decline, perish”), with the Proto-Indo-European cluster *dʰgʷʰ- metathesizing into pre-Italic *gʷʰdʰ-, yielding *kts- and finally Latin s-. Cognates include Sanskrit क्षिति (kṣíti, “perishing, downfall”) and Ancient Greek φθίσις (phthísis, “decrease, emaciation”).