In its defense, he was made up for the Star Wars Holiday Special, which is notoriously awful, but then he was worked into comics, children's stories, novels... Of course, no longer canon, but honestly, who thought this was a good idea? Chewie also had a father named Attichitchuk... nicknamed Itchy.

Oh hey, I was double-checking Lumpy's entry on wookiepedia, and apparently his nickname changes to Waroo as an adult, because apparently he realized that Lumpy is a terrible nickname. Hah! I vote that Ben still calls him Lumpy in private, just to annoy him. They are like brothers.