Who discovered thermal energy?

While i was looking for some information to post, a question came to mind: Who discovered thermal energy?
thermal energy was discovered by James Prescott Joule was born on December 24^th, 1818 & died on October 11^th, 1889. He was an English physicist who recognised the transfer of energy  from a heat source into other materials such as water when it boils.
He found that when he agitated the fluid, its temperature increased. Joule performed mechanical work on the fluid and in doing so, converted that mechanical energy to thermal energy.
here´s a picture of James.

carlos.