Faulkner used the Snopes family to represent the dark side of the "new" (post civil war) south as opposed to the south of antebellum mythology (e.g. "Gone With the Wind").

Everything you could possibly want to know:
http://www.mcsr.olemiss.edu/~egjbp/faulkner/glossarys.html#Snopes

The person who named the sight must've been an English Major.