|An 1897 encyclopedia definition of thermodynamicist, defined as a student of or one versed in thermodynamics.  In 1891, William Magie was described as a “thermodynamicist trained by Helmholtz”. (Ѻ)|
A closely related term to thermodynamicist, generally a post 1940s term, was "energeticist", a term of the late 19th century. American Willard Gibbs, for instance, was often referred to as an energeticist; whereas, in modern terms, he is considered a chemical thermodynamicist or more specifically the "founder of chemical thermodynamics".  In the 1890s, by comparison, German energeticist Wilhelm Ostwald, often considered as the founder of the "school of energetics", who had recently translated Gibbs' On the Equilibrium of Heterogeneous Substances into French, styled Gibbs as the "founder of chemical energetics". 
The following is a noted quote, that seems to have originated in originated with Percy Bridgman (1941), regarding how there is a different version of the first law and or second law for ever thermodynamicist: 
“There’s as many formulations of the second law as there have been discussions of it.”
This was rephrased by Clifford Truesdell (aware or not of the Bridgman-version) in 1969 as follows: 
“I hesitate to use the terms ‘first law’ and ‘second law’, because there are almost as many ‘first laws’ as there are thermodynamicists, and I have been told by these people for so many years that I disobey their laws that now I prefer to exult in my criminal status and non-condemning names to the concrete mathematical axioms I wish to use in my outlaw studies of heat and temperature. The term ‘entropy’ seems superfluous, also, since it suggest nothing to ordinary persons and only intense headaches to those who have studied thermodynamics but have not given in and joined the professionals.”
This has since come to be known as:
“There’s as many version of the second law as there are thermodynamicists.”
This last version, supposedly, began to be used in the 1950s. 
● Human thermodynamicist
● Thermodynamicist (other)
● Thermodynamics founders
● Human thermodynamics pioneers
1. Perrot, Pierre. (1998). A to Z of Thermodynamics (pg. 312). Oxford: Oxford University Press.
2. Nemilov, Sergei V. (1995). Thermodynamic and Kinetic Aspects of the Vitreous State (pg. 5). CRC Press.
3. Willard Gibbs - Encyclopedia Britannica article (1910).
4. Bridgman, Peter W. (1941). The Nature of Thermodynamics (pg. 116). New York: Harper Torchbooks.
5. (a) Truesdell, Clifford A. (1969). Rational Thermodynamics: A Course of Lectures on Selected Topics (pg. 11). Springer-Verlag.
(b) Gal-Or, Benjamin. (1974). Modern Developments in Thermodynamics: an Interdisciplinary Collective Treatise (§: Thought-Provoking and Thought-Depressing Quotations” (43 quotes selected by B. Gal-Or), pgs. 435-42). Wiley.
6. 110+ versions of the second law (note 1) – HumanThermodynamics.com.
7. Whitney, William D. and Smith, Benjamin E. (1897). The Century Dictionary and Cyclopedia: a work of universal reference in all departments of knowledge, with a new atlas of the world, Volume 8 (pg. 6282). Century.
● Fleeter, Rick. (2007). Travels of a Thermodynamicist. Outskirts Press.
● Category: Thermodynamicists – Wikipedia.