Banana Connectors
From YourSpec Automotive Wiring Wiki
Banana Connectors, (commonly banana plugs for the male, banana jacks (or banana sockets) for the female, or 4mm Connectors(Europe)), are round, single conductor connectors widely used in test equipment, power supplies, and audio connections. A sheathed version of the 4mm banana plugs is commonly used on multimeter probe leads. Both Hirschmann and General Radio Company claim to have invented the Banana Connector in the 1920s.
Today, Banana Connectors are available from companies such as Mueller Electric, Pomona, Electro-PJP (Europe), Amphenol, and Keystone.
