Blaggard

blaggard /ˈblægəd/ noun: 1. a scoundrel; an unprincipled, contemptible person; an untrustworthy person (usually male) 2. a man who uses foul language

Etymology: English blackguard

A blackguard was a kitchen servant in a large house (perhaps so called from working in dark quarters or getting besmirched with soot from the fireplace.) Through metonymy blackguard came to mean any person exhibiting those characteristics typically displayed by kitchen staff. Are cooks getting a bad rap? Perhaps.