From Proto-Indo-Iranian *tāpás, from Proto-Indo-European *tep-. Cognate with Sanskrit तपस् (tapas, “heat, fire”), Persian آفتاب (âftâb, “sun”), Persian تاب (tâb, “heat, warmth”), Ormuri تووه (“sun”), Latin tepidus (“warm”), Russian тёплый (tjóplyj, “warm”), Old Armenian տապ (tap, “heat”).