The term "leatherneck" was derived from a leather stock once worn around the neck by both American and British marines. Beginning in 1798, "one stock of black leather and clasp" was issued to each marine annually. Its use as a synecdoche for Marines began as a term of ridicule by sailors.
This stiff leather collar, fastened by two buckles at the back, measured nearly three and a half inches high, and it prevented the neck movement necessary for sighting along a barrel. The origin of the leather neck collar has to do with early 19th Century military fashion trends in Europe and North America. Its use among enlisted men supposedly improved their military bearing and appearance by forcing the chin high and to serve as protection for one's neck from sword blows by Muslim pirates . General George F. Elliott, recalling its use after the Civil War, said it made the wearers appear "like geese looking for rain."
The stock was dropped as an article of marine uniform in 1872, after surviving through the uniform changes of 1833, 1839, and 1859.
^Lighter, Jonathan (June 20, 2014). "How World War I gave us 'cooties'". CNN. Retrieved 2014-06-22. "Now accepted by Webster as a synonym for Marine, the term "Leatherneck" was derived from a leather stock once worn around the neck by both American and British Marines--and soldiers also. Beginning in 1798, "one stock of black leather and clasp" was issued to each U. S. Marine annually."
^"Lore of the Corps". National Museum of the Marine Corps. Retrieved 2014-06-22. "This leather collar served to protect the neck against cutlass slashes and to hold the head erect in proper military bearing. Sailors serving aboard ship with Marines came to call them 'leathernecks.' Use of the leather stock was retained until after the Civil War when it was replaced by a strip of black glazed leather attached to the inside front of the dress uniform collar. The last vestiges of the leather stock can be seen in today’s modern dress uniform, which features a stiff cloth tab behind the front of the collar. The term 'leatherneck' transcended the actual use of the leather stock and became a common nickname for United States Marines."