I like this joke, not an answer but funny:
A young Ensign approached a crusty old Master Chief and asked about the origin of the commissioned officer insignias.
"Well," replied the Master Chief, "the insignias for the Navy are steeped in history and tradition.
As an Ensign, we give you a gold bar, representing that you are very valuable but also malleable.
The silver bar of a Lieutenant Junior Grade also represents significant value, but is less malleable. Now, when you make Lieutenant, your value doubles, hence the two silver bars.
As a Captain, you soar over the common sailors, hence the eagle. And when you make Admiral, you are obviously a star.
Does that answer your question?"
"Yes, Master Chief," replied the young Ensign. "But what about Lieutenant Commanders and Commanders?"
"That, Sir, goes waaaay back in history - back to the Garden of Eden. You see, we've always covered our pricks with leaves."