Oddly enough, "starbuck" has nothing to do with stars. It comes from some Old Norse meaning "sedge river". This became the place name Starbeck, a town in northern England. People then took that as a surname, and the spelling changed to Starbuck at some point. Herman Melville then gives a character in Moby Dick the surname Starbuck, and eventually the founders of the coffee chain picked it for no particular reason other than that they liked the sound of it
So the "buck" part is, I guess, "river". Or "brook", to pick the more closely-related English term. This doesn't change anything you said, of course, as nobody actually thinks of it like that, I just found the winding path it took kinda interesting