before vowels therm-, word-forming element meaning "hot, heat, temperature," used in scientific and technical words, from Greek thermos "hot, warm," therme "heat" (from PIE root *gwher- "to heat, warm").
word-forming element meaning "process of writing or recording" or "a writing, recording, or description" (in modern use especially in forming names of descriptive sciences), from French or German -graphie, from Greek -graphia "description of," used in abstract nouns from graphein "write, express by written characters," earlier "to draw, represent by lines drawn," originally "to scrape, scratch" (on clay tablets with a stylus), from PIE root *gerbh- "to scratch, carve" (see carve).
<a href="https://www.etymonline.com/word/thermography">Etymology of thermography by etymonline</a>
Harper, D. (n.d.). Etymology of thermography. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/thermography