In life, there are moments of truth. And in those moments, the question is always the same. "Am I ready?" Marines are always ready.
Nick names
Devil Dog :,A Marine. The name "Teufel Hundin" was given to the Marines by their German enemies in World War I, probably as an insult since hunden translates more correctly as "bitch". It has come to be considered a sign of respect for the dogged determination of Marines. 
Leatherneck: The nickname Leatherneck has become a universal moniker for a U.S. Marine. The term originated from the wide and stiff leather neck-piece that was part of the Marine Corps uniform from 1798 until 1872. This leather collar, called The Stock, was roughly four inches high and had two purposes. In combat, it protected the neck and jugular vein from cutlasses slashes. On parade, it kept a Marine's head erect. The term is so widespread that it has become the name of the Marine Corps Association monthly magazine
Gyrene: Around 1900, members of the U.S. Navy began using Gyrene as a jocular derogatory reference to U.S. Marines. Instead of being insulted, the Marines loved it. The term became common by World War I and has been extensively used since that time.
Jarhead: For roughly 50 years, sailors had little luck in their effort to insult Marines by calling them Gyrenes. So, during World War II sailors began referring to Marines as Jarheads. Presumably the high collar on the Marine Dress Blues uniform made a Marine's head look like it was sticking out of the top of a Mason jar. Marines were not insulted. Instead, they embraced the new moniker as a term of utmost respect.
Soldiers of the Sea: A traditional and functional term for Marines, dating back to the British in the 1600's