When was the phrase "beta function" of renormalization first used?

I've seen references specifically to the "Callan-Symanzik beta function", so I don't think it was much later. (Curt Callan and Kurt Symanzik independently discovered their equation in 1970.) Although the notation of Callan (1970) is unclear to me, Symanzik (1970) implicitly defined $beta(g)$ [Eq. (I.13)] Then, Symanzik (1971) clearly defined $beta(g)$ as a derivative [Eq. (I.13b)] and discussed some of its properties. Symanzik simply named different coefficients $alpha,beta,gamma$, so the notation itself is rather natural.

The earliest published instances I'm aware of where the function was referred to by the phrase (as opposed to "$beta(g)$", "the function $beta$", or similar) are from a couple years later. Politzer (1973) stated that the notation was already common "the coefficient function in the Callan-Symanzik equations commonly called $beta(g)$...", and proceeded to explicitly write "$beta$ functions". Later the same year, Weinberg (1973) did use "beta function" in text form. I cannot rule out someone else using the phrase earlier, but it nevertheless appears to be during the early 70s.