1840, "method of writing which requires heat to develop the characters," from thermo- + -graphy.
Entries linking to thermography
thermo-
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").
-graphy
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).