Wild-ass guess #1: the term "Leatherneck," used in US for a Marine, derives from their having worn leather collars in the Good Old Days, point being to ward off sword slashes, bayonet thrusts, and other of the more unpleasant results of being silly enough to join the Marines. Can't say without more lyrics, but is there any military connection?? I doubt if the US Marines were ever the first ones to think of anything.

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