The U.S. military services still use many of the ranks they started with when they began in 1775 at the start of our Revolutionary War. The leaders adopted the organization, regulations and ranks of the British army and navy with just minor changes. This is not surprising because our Revolutionary Army was made up of colonial militia units that had been organized and drilled by British methods for many years. Most of the military experience of the soldiers and their officers, George Washington among them, had come from service in militia units fighting alongside British army units during the French and Indian War of 1754-1763.
The British navy was the most successful in the world at that time so the Continental Congress' navy committee, headed by John Adams who became President after Washington, copied it as they set up our Navy. They adopted some British regulations with hardly a change in the wording. Our first Marine units patterned themselves after British marines.
Revolutionary Army rank insignia, however, did not follow the British patterns but was similar to the insignia used by the French, our allies after 1779. After the war our Army often used the uniform styles and some insignia of the British as well as the French armies. During the latter part of the Nineteenth Century German army styles also influenced our Army's dress. Our Navy used rank insignia and uniforms similar to the British navy's during the Revolutionary War and afterwards. Marine rank insignia has usually been similar to the Army's, especially after 1840.
The Coast Guard dates from 1915 when Congress combined the Revenue Cutter Service, which started in 1790, with the U.S. Life Saving Service. During World War I Coast Guard ranks became the same as the Navy's. The Air Force started as a separate service in 1947. Its officers use the same ranks and rank insignia as the Army. I will discuss the enlisted rank insignia later.
The basic names for members of the military professions go back several centuries. A Seaman's occupation is on the sea and his name, from an Old English word that was pronounced see-man, means a person whose occupation is on the sea. A Sailor is a person professionally involved with navigation or sailing. His name, which comes from the Old English word saylor, means just that, a person professionally involved with navigation. A Marine gets his name from the Latin word marinus, which means something pertaining to the sea. A Soldier is a person who serves in a military force for pay. His name comes from the Latin soldus, a contraction of another Latin word solidus, a Roman coin used for, among other things, paying military men.