As a common noun, English heat or warmth (just as French chaleur, German Wärme, Latin calor, Greek θάλπος, etc.) refers to (the human perception of) either thermal energy or temperature. Speculation on thermal energy or "heat" as a separate form of matter has a long history, identified as caloric theory, phlogiston theory, and fire.
Heat has been discussed in ordinary language by philosophers. An example is this 1720 quote from John Locke:
:::::Heat, is a very brisk agitation of the insensible parts of the object, which produces in us that sensation from whence we denominate the object hot; so what in our sensation is heat, in the object is nothing but motion. This appears by the way, whereby heat is produc’d: for we see that the rubbing of a brass nail upon a board, will make it very hot; and the axle-trees of carts and coaches are often hot, and sometimes to a degree, that it sets them on fire, by the rubbing of the nave of the wheel upon it.
This source was repeatedly quoted by Joule.
John Tyndalls Heat Considered as Mode of Motion' (1863) was instrumental in popularizing the idea of heat as motion to the English-speaking public.
The theory was developed in academic publications in French, English and German. From an early time, the French technical term chaleur used by Carnot was taken as equivalent to the English heat and German Wärme (lit. "warmth", while the equivalent of heat would be German Hitze).