Well, "moon" as a verb is a recent innovation. Webster gives the earliest use as 1836, meaning to dream or spend time in idle reverie.

But the dictionary doesn't give a date for the "moon" use as flashing the derriere. (The Constitution and the Derriere???)

I'm betting that slang usage isn't older the 1960s. I first heard it used in connection with Jim Morrison of the Doors, and that was late 1960s. I didn't hear it in connection with the occasional dropping of the drawers (the term then common) to flash people during college days in the late 1950s.

So I think the song above has to be a post-1960 composition. To me its imitation of older phraseology sounds like common parlance of the 1980s or later. "Shelve" in this sense, for example ... "the American way" ... and so on.

Bob