Chernykh, P. Ja. (1993) “тёплый”, in Историко-этимологический словарь русского языка [Historical-Etymological Dictionary of the Russian Language] (in Russian), 3rd edition, volumes 2 (панцирь – ящур), Moscow: Russian Lang., →ISBN, page 236
Vasmer, Max (1964–1973) “топи́ть”, in Oleg Trubachyov, transl., Этимологический словарь русского языка [Etymological Dictionary of the Russian Language] (in Russian), Moscow: Progress
Unclear. Vasmer suggests a possible connection with Old Armenianթաթաւեմ(tʻatʻawem, “to soak (e.g. clothes in blood)”), but notes that it's quite conjectural. Trubachev notes that Zubaty and Stang suggest a connection with Lithuaniantàpti(“to become”), Latviantapt(“to become, to get infected”), effectively from Proto-Balto-Slavic*taptéi(“to get stuck”) + *-iti.
^ Derksen, Rick (2008) “*topìti II”, in Etymological Dictionary of the Slavic Inherited Lexicon (Leiden Indo-European Etymological Dictionary Series; 4), Leiden, Boston: Brill, →ISBN, →ISSN, page 496
^ Snoj, Marko (2016) “-topiti”, in Slovenski etimološki slovar [Slovenian Etymology Dictionary] (in Slovene), 3rd edition, https://fran.si: “Pslovan. *topi̋ti ‛potapljati’”
Vasmer, Max (1964–1973) “топи́ть”, in Oleg Trubachyov, transl., Этимологический словарь русского языка [Etymological Dictionary of the Russian Language] (in Russian), Moscow: Progress