Green’s Dictionary of Slang

(US) a derog. term for a peasant.

1970		E. Thompson Garden of Sand (1981) 273: He personally viewed everyone out of prison as peapickers, hoosiers, hayseeds, or clodhoppers.
1977		J. Sayles Union Dues (1978) 206: Its title comes from the words of the old pea-picker himself, Cowboy Karl Marx.