The term "second banana" is an idiomatic expression that refers to a person who plays a supporting role or is subordinate to another. It can be used in various contexts, such as referring to someone who is second-in-command, a backup singer, or even a sidekick. The phrase originated from the fact that bananas are often sold in pairs - with one larger, riper fruit being marketed as the primary item and the smaller, greener one serving as its secondary counterpart. In this sense, "second banana" implies someone who is less important or prominent than another person but still plays a crucial role in their success.