Who coined the term "gas evolution reaction"?
There is no specific term as &quot;gas evolution reaction&quot; in modern chemistry but the word evolve itself conveys this meaning of emission. I am curious as to why you are interested in this terminology? Just for the sake of historical interest, the unabridged Oxford Dictionary (subscription required) shows that the term dates back to 1770s in relation to gas, heat, light etc. However there is no guarantee that the following references are the earliest. If you have more energy or you are a serious scholar of history, you might need to see German and French literature before the 1770s and what words Lavoisier used when he heated the oxide of mercury and discovered oxygen.

IV. The process of emission.

Chiefly Chemistry. The emission or release of gas, heat, light, etc.; the disengagement of a substance from combination; an instance
of such a process. Cf. evolve v. 5.

1783   Philos. Trans. (Royal Soc.) 73 350   The method put in practice
by Mr. Hutchins to settle the freezing point of quicksilver depends
entirely upon this generation, re-appearance or evolution of heat.
1800   H. Davy Res. Nitrous Oxide 425   This is on account of the
increased evolution of nitrogene from the blood.

Similarly, evolve is even older

1772   [implied in: J. MacLurg Exper. Human Bile 38   The colouring
matter of the Bile discovers also a much stronger attraction to the
mineral acids, and gives indubitable marks of a more evolved
phlogiston. (at evolved adj. 2)].
1786   Edinb. New Dispensatory i. 7   In the incipient state a
quantity of gas is still evolved, and along with it a quantity of
alkaline air.