A worn-out wig; also a big cauliflower wig, worn out or not. It has been suggested that the word is from the proper name, but nothing whatever is known about such a person.
People scarce could decide on its phiz, Which looked wisest- the caxon or jowl.
Peter Pindar: The Portfolio.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894