Final answer:
The high collar on the Marine Dress Blues has earned U.S. Marines the nickname "Leathernecks," underlining the connection between military uniforms and discipline.
Step-by-step explanation:
The nickname given to the U.S. Marines due to the high collar on their Dress Blues is “Leathernecks”. This distinct feature of the Marine uniform has a long history and is associated with the immaculate appearance and disciplined posture that the uniform encourages. George Washington emphasized the importance of appearance and authority in military uniforms, a tradition that has been carried on through various interpretations like the Continental Army uniform, and further exemplified by the striking presence of military dress in historical paintings and portrayals of key figures such as Napoleon.