Green’s Dictionary of Slang

rural, small-town, rustic.

1937		E. Anderson Thieves Like Us (1999) 8: I’m not going to fool with any of these clodhopper town banks.
1955		E. Hoagland Cat Man 144: Bible’s boots were crossed a few inches to the left of Fiddler’s head, one heel gouged into the ground; big clodhopper boots.
1984		W. Diehl Hooligans (2003) 219: A faded cotton shirt, clodhopper boots.