I was in the first H-46 squadron deployed to Vietnam, Hmm-164. (YT) "Watson's Warriors" at Marble Mountain. I don't remember hearing the term "Phrog" at that time. But then again there's a lot I don't remember about that first go round, Too many night med-evacs!
The 2nd trip over, I flew H-34's as a "Purple Fox" in HMM-364 (PF) for a few months. We spent our free time trying to sneak around and paint, using a stencil of a fox on every vehicle any other outfit owned with purple paint of course. As I recall, we stenciled about a dozen Jeeps from various other outfits during one big meeting held by Lt. General Walt.
Soon after that episode, mid deployment and maybe having to do with the spray paint job, I was transferred back to 46's in HMM-165. (YW) I remember that positing really well. It's when I broke my neck in a very hard landing caused by almost no hydraulic pressure, which sent me home and out of the Corps for good.
I'm guessing the term "Phrog" came along after I was out.
Michael