blackguard

The word "blackguard" originated in the early 16th century, not as a term for a villain, but as a collective noun for the lowest menials in a royal or noble household, such as kitchen scullions and pot-boys who guarded the pots and pans. These individuals, often sooty from working with cooking fires, were literally the "black guard." Over time, the term's association with low status and menial, often disreputable, characters caused its meaning to shift. By the 18th century, it had fully evolved into a term of abuse for a scoundrel or someone of contemptible character, completing the journey from a literal description of a dirty retinue to an abstract insult denoting moral foulness.

Structure: black + guard - black: From Old English blæc, meaning "dark, without light." In this compound, it carries the figurative sense of "evil, wicked." - guard: From Old French garder, meaning "to watch, keep, protect." In this compound, it refers to a person with a duty.