Green’s Dictionary of Slang

a potato; thus croker sack n., potato sack.

1934		E. Caldwell Tobacco Road (1958) 13: What you got in that there croker sack, Lov?
1948		Z.N. Hurston Seraph on the Suwanee (1995) 849: Even in a croker-sack, Angeline would look like their mistress.