Do you know why Marines are called Leather Necks?

[Booher]

Leatherneck: A U.S. Marine. (The Marine uniform originally had a leather-lined collar.) Since the days of the Barbary pirates, U.S. Marines have called themselves "leathernecks." Legend and lore have it that the term leatherneck was derived from leather neckbands worn in the late 1700s to protect Marines from the slash of the cutlass. Another more likely reason is that the high stocks were worn for discipline to keep the Marines' heads high and straight. Neither explanation has ever been verified. Whatever the reason, the name leatherneck stuck and the distinctive dress blue uniform blouse still bears a high stock collar to remind Marines of the leatherneck legacy.