The origin of "m"?

[Quadratic]

Why is it that linear functions are often expressed in terms of f(x)="m"x+b? I mean, when dealing with all the other polynomials, we follow the typical f(x) = ax^n + bx^(n-1) + cx^(n-2)... so where did "m" come from? Why don't all text books just express it as f(x) = ax+b?

[jcsd]

J. Miller has undertaken a detailed study of the origin of the symbol m to denote slope. The consensus seems to be that it is not known why the letter m was chosen. One high school algebra textbook says the reason for m is unknown, but remarks that it is interesting that the French word for "to climb" is "monter." However, there is no evidence to make any such connection. In fact, Descartes, who was French, did not use m (Miller). Eves (1971) suggests "it just happened."

http://mathworld.wolfram.com/Slope.html