Carl ‘Nibs’ Cotton

The name Carl comes from Old English, referring to a specific low rank of freeman. The original form was Ceorl, and indeed that form of the name is recorded as being used among the Rohirrim. Both Carl and Ceorl represent translations of the characters' original names from the language of the Northmen, and given their common origins, the original (unrecorded) forms in Middle-earth would also presumably have been similar to one another.

Carl's nickname of 'Nibs' is not explained, though in common use, 'nibs' refers to a person with an inflated sense of their own importance (especially in an expression like 'his nibs'). Lacking a direct explanation of the name, it's impossible to say whether this modern sense was intended by Tolkien as any kind of insight into Carl's personality.