Who is Prof. John MacWalsey from To Have and Have Not and what is their importance?

Prof. John MacWalsey is described as having a swollen red face, a rusty-colored mustache, and a hat with a green celluloid visor. He finds a fellow tourist and drinker at Freddy's bar to be charming for due to her use of the obsolete word "nerts." The two chat amiably before MacWalsey bicycles away.

MacWalsey is an economics teacher on sabbatical and a friend of Helen Gordon. Richard Gordon later finds MacWalsey with his wife, and the spouses have an arguement that subsequently ends their marriage.