When functions $f$ and $g$ have the property that $f(g(x)) = g(f(x))$ for all $x$ in the domains I call this property 'commutativity'. (usually both functions map from $\mathbb{R}$ to $\mathbb{R}$, so the problem of domain/range doesn't matter)
However, commutativity is actually when: $a*b=b*a$
I use it knowing that it probably isn't the right term... but I've never found out what I should call it.