What is the meaning of Gudgeon?

A small freshwater fish, Gobio gobio, that is native to Eurasia.

Cottus bairdii, more widely known as mottled sculpin.

Any of various similar small fish of the family Eleotridae, often used as bait.

Other fish, similar in appearance, principally in families Butidae and Eleotridae, but also in others.

A person apt to take the bait; one easily cheated or duped; also, an idiot.

Something used to lure or tempt; bait, a lure.

To deprive (someone) fraudulently; to cheat, to dupe.

To take the bait; to be defrauded or duped.

A circular or cylindrical fitting, often made of metal, into which a pin or pintle fits to create a hinge or pivoting joint.

In a vessel with a stern-mounted rudder: the fitting into which the pintle of the rudder fits, allowing the rudder to swing freely.

Source: wiktionary.org