'heat-stimulus' originates from the combination of 'heat' and 'stimulus', where 'heat' refers to warmth or high temperature, and 'stimulus' refers to something that incites a response.

'heat-stimulus' combines the Old English word 'hǣtu' for 'heat' and the Latin word 'stimulus' meaning 'goad' or 'spur'.

Initially, it referred to any form of heat that incited a response, and this meaning has largely remained the same in modern usage.