Gudgeon pin

In internal combustion engines, the gudgeon pin (UK, wrist pin US) connects the piston to the connecting rod and provides a bearing for the connecting rod to pivot upon as the piston moves. In very early engine designs (including those driven by steam and also many very large stationary or marine engines), the gudgeon pin is located in a sliding crosshead that connects to the piston via a rod. A gudgeon is a pivot or journal. The origin of the word gudgeon is the Middle English word gojoun, which originated from the Middle French word goujon. Its first known use was in the 15th century.