mudsill

A mudsill is the lowest timber of a structure, resting directly on the ground or foundation—the base that supports everything above it.

The term became a political epithet in antebellum America when Southern defenders of slavery argued that every society needs a degraded class to do its dirtiest work, a "mudsill" upon which civilization rests.

The theory held that enslaved Black people served this function better than Northern wage laborers.

The word still occasionally surfaces in discussions of class and exploitation: Every economy has its mudsills, the workers no one wants to acknowledge.