Green’s Dictionary of Slang

a clumsy fool.

1834		‘The Blowen’s Ball’ in Bang-Up Songster 5: They proved they were none of them guffins.
1842		J. Labern ‘The Larned Dustman’ Comic Songs 28: The Wote by Ballads I admire, / And them as don’t are guffins.
1879		Ouachita Teleg. (Monroe, LA) 11 July 1/5: When a St Louis girl gets married [...] the terms [...] ‘guffins’ and ‘corn-planters’ are applied in the most reckless manner.
1895		‘’Arry and the New Woman’ in Punch 18 May 230/3: The jawsome old guffin wos right [...] leastways she wosn’t fur out.
1934		Wodehouse Right Ho, Jeeves 101: Augustus Fink-Nottle was nature’s last word in cloth-headed guffins.
1954		Wodehouse Jeeves and the Feudal Spirit 114: She says you are a guffin [...] It’s one of those old-fashioned expressions.
1960		Wodehouse Jeeves in the Offing 29: Cannot understand how you can be contemplating marrying that guffin.