Chump

"chump" is a slang term for a person who is unschooled or unaware, often used to indicated someone deluded and misdirected.

The phrase is derived from a brand of Australian dog food advertised as "So chumpy you could carve it". A chump therefore has the connotations of being thick and unwitting. Uncarveable chumpiness denotes a certain stubborness and adherence to a misguided doctrine.