The story
- Proto-Indo-European*gʷʰer-
- Proto-Indo-European*gʷʰermos
- Proto-Hellenic*kʷʰermós
- Ancient Greekθερμός (thermós)
- Englishthermo-
- Proto-Indo-European*h₂eǵ-
- Proto-Indo-European*h₂éǵeti
- Proto-Italic*agō
- Latinagō
- Ancient Greekἐνεργητικός (energētikós)
- Latināctīvu
- Old Frenchactif
- Middle Englishactyf
- Englishactive
- Englishactivate
- Englishactivation
- English todaythermoactivation
From thermo- + activation.
Etymology from Wiktionary, CC BY-SA 4.0.