What is the name of Scooby-Doo's dim-witted cousin?

Scooby-Doo's dim-witted cousin is named Scooby-Dum.

Scooby-Dum is a Great Dane character who appears as Scooby-Doo's cousin in the wider franchise. He lives in the Okefenokee Swamp and is characterized as even less clever than Scooby-Doo, providing a comic contrast to the main dog. His name is a pun on “Scooby-Doo” and the word “dumb,” matching his intentionally foolish personality.

Scooby-Dum was voiced by Alan Oppenheimer and later appeared in Laff-A-Lympics, where Daws Butler provided his voice. Like Scooby-Doo, he is involved in exaggerated cartoon adventures rather than the grounded mystery-solving format of the original gang's stories.

Viewers sometimes confuse Scooby-Dum with Scooby-Dee, another canine relative. Scooby-Dee is a white Great Dane and a distant cousin who appears in The Scooby-Doo Show. Yabba-Doo is also related to the family, but he is Scooby-Doo's brother, while Scrappy-Doo is Scooby-Doo's nephew. Those relationships make the similar names easy to mix up, but Scooby-Dum is the canonical answer to this question.