Etymology tree Proto-Indo-European *tep- Proto-Indo-European *-éh₁ti Proto-Indo-European *-yeti Proto-Indo-European *-éh₁yeti Proto-Indo-European *t(e)péh₁yeti Proto-Italic *tepēō Latin tepeō Proto-Indo-European *dʰeh₁-der. Proto-Italic *-iðos Latin -idus Latin tepidusbor. English tepid Borrowed from Latin tepidus. Cognate with Sanskrit तप् (tap), Proto-Slavic *teplъ.