The young Ensign approached the crusty old Chief and asked him about the origin of the commissioned office insignias.

"Well, Ensign, it's history and tradition. First, we give you a gold bar representing that you're valuable BUT malleable. The silver bar of a Lieutenant Junior Grade represents value, but less malleable. When you make Lieutenant, you're twice as valuable so we give you two silver bars.

"As a Captain, you soar over military masses, hence the eagle. As an Admiral, you're obviously a star. That answer your question?"

"Yeah, but what about Commanders and Lieutenant Commanders?"

"Now that goes waaaaaay back in history. Back to the Garden of Eden even. You see, we've always covered our pricks with leaves... "