Green’s Dictionary of Slang

barndoor savage n.

a rustic, a yokel.

1876		C. Hindley Life and Adventures of a Cheap Jack 46: Sold again, to the barn-door savage. Look at him. What a capital face he’s got to frighten little children.
1942		Berrey & Van den Bark Amer. Thes. Sl. §391.3: rustic; bumpkin, barndoor savage.