Green’s Dictionary of Slang

a fool, a yokel; thus attrib.

c.1534		P. Vergil Eng. Hist. (translation) (1846) I 285: Fallinge into [...] altercation with a stronge stubberne clomperton, he was shrowdlie beaten of him [N].
1589		J. Throckmorton Godly treatise 54: [I]t puts me in minde of a litle pretty story, that we haue of a scholler of Oxford, and a Clumperton of the Cuntry.
1599		R. Perceval A dictionarie in Spanish and English 273: a Clowne or clumperton, vide Capatáz, Villáno.
1608		H. Clapham Errour on the right hand 15: [A]n olde clumperton paire of Shooes [...] as my brother George Clayton the Brick-layer had.
1677		E. Coles An English dictionary n.p.: Clumperton, a clown.
1822		R. Nares Gloss. (1888) I 167: †clomperton. A clown.
1870		All the Year Round 5 Mar. ‘Byegone Cant (Geo. II) n.p.: Clumpertons agape at the giant proportions of the still somewhat new St. Paul’s would turn from their wondering walks to shudder and shrink at the ghastly gallows exhibition at Newgate [F&H].
1877		Sussex Advertiser 23 June 4/6: That bag had something in it worth nailing [...] but you, you cursed ninny, coolly handed it back to the clumperton.