'geothermic' originates from Greek combining forms: 'geo-' from Greek 'gē' meaning 'earth' and 'therm-' from Greek 'thermos' meaning 'heat', with the adjective-forming suffix '-ic'.

'geothermic' developed in scientific English alongside and after terms like 'geothermal' (from the 19th century); it was formed by combining the classical elements 'geo-' + 'therm-' plus '-ic' to create an adjective used in descriptions of Earth's heat-related phenomena.

Initially it meant 'of or relating to the Earth's heat'; over time this technical meaning has remained stable and is still used primarily in scientific and engineering contexts to describe processes, energy, or properties involving Earth's internal heat.