Who introduced the term 'thermodynamics' in an 1849 paper?

William Thomson introduced the term “thermo-dynamic” in an 1849 paper, making him the standard answer to this historical question about the origin of “thermodynamics.” Thomson was the Scottish-Irish physicist later known as Lord Kelvin.

His paper, “An Account of Carnot’s Theory of the Motive Power of Heat,” discussed Sadi Carnot’s theory and the relationship between heat and mechanical work. Thomson’s terminology helped establish thermodynamics as the name for the developing science of heat engines, energy conversion, and thermal processes.

There is a small historical wording trap. In 1849 Thomson used the adjective “thermo-dynamic”; the noun “thermo-dynamics” became established in later usage, including work by Thomson and William Rankine in 1854. Some histories also discuss claims involving James Joule, but Joule did not consistently use the noun and referred instead to a “perfect thermo-dynamic engine.”