When calculus was first being developed, the terms "fluent" and "fluxion" appeared quite often in the Newtonian works.
I am wanting to know the etymology behind these words. I assume that "fluents" are related to the concept of "fluid" or "flowing", but (as far as I am aware) the word has gone out of usage in mathematics.
"Fluxions" are not used in modern-day texts, but I assume that "flux" (a term with which every physics student will be familiar) derives from "fluxion".
If context helps, one would usually talk of a "fluent" as a moving point, generating a curve, and a "fluxion" as its velocity (direction + speed). I am interested in knowing why these terms were used, and what they referred to.
EDIT: On a related note, Newton writes "Fluxions of quantities are in the first ratio of their nascent parts or, what is exactly the same, in the last ratio of those parts as they vanish by defluxion." What would "defluxion" refer to?