What or who is a scullion? (From Shakespeare's Hamlet)

A scullion is a kitchen helper.

Why, what an ass am I! This is most brave, / That I, the son of a dear father murdered, / Prompted to my revenge by heaven and hell, / Must (like a whore) unpack my heart with words / And fall a-cursing like a very drab, / A scullion!

From Shakespeare's Hamlet.