What does the term "Leatherneck" signify in relation to Marines?

The term "Leatherneck" signifies a nickname for Marines, which originates from the historical leather collars that were part of the Marine Corps uniform in the 18th and 19th centuries. These collars were designed to protect the throat of the Marines during battles and to maintain a stern posture. Over time, the term evolved into a moniker that represents the Marine Corps' proud heritage and tough demeanor. The use of "Leatherneck" embodies the spirit of resilience and camaraderie that is significant to Marine identity. The other options do not capture the cultural and historical significance that this nickname has within the Marine Corps.