'athermancy' is a modern English formation built from the Greek-derived prefix 'a-' meaning 'not' or 'without' and the combining form 'therm-' (from Greek 'thermē') meaning 'heat', plus the English nominal suffix '-ancy' (from Latin/French suffixes meaning a state or quality).

'athermancy' does not have a long historical lineage in classical English; it is a coinage formed in modern English from Greek elements ('thermē' → 'therm-') with prefix 'a-' and suffix '-ancy', modeled on other abstract nouns (e.g., 'vacancy').

Originally construable simply as 'absence of heat' from its elements, its usage in speculative and fictional contexts has specialized to denote an ability or magical discipline that negates or controls heat.