What are banana plugs? They are visually distinctive cylindrical connectors for electrical wiring.
The name is a reference to a protruding prong that bulges slightly in the centre, called a banana due to its supposed resemblance to the fruit. This contains a spring-mounted fin that expands once it has been inserted into an equipment socket, creating a firm and potentially permanent hold.
Banana plugs were invented in 1924 by German engineer Richard Hirschmann, although now-defunct US company General Radio made a competing claim.
They are also known as banana connectors and 4mm connectors. The latter is a reference to a standard diameter.