[Air-L] History and origins of diffusion processes

If one looks up the word 'diffusion' in the *Dictionary of the History of Science*, you get the standard explanation that 'diffusion' originated in the 19th c with Graham and Maxwell and has a Latin etymology in the word, *diffundere*, which means "to spread out." There has to be more to the story than this, right? Earlier references might include the "diffusion of refracted light" in Robert Greene (1727) and "diffusion of light" in Newton's *Optical Lectures* (1728). My question for these listservs is, does anyone have any additional insight into the history and origins of the abstract idea of 'diffusion?' Thank you, Thomas Ball