mudsill

Etymology
"1685, 'lowest sill of a house,' from mud + sill. The word entered U.S. political history in a speech by James M. Hammond of South Carolina, March 4, 1858, in U.S. Senate, alluding to the very mudsills of society, and the term subsequently was embraced by Northern workers in the pre-Civil War sectional rivalry." (OED, 2007)

Noun

 * 1) The lowest sill of a structure, usually placed in or on the ground.
 * 2)  A particularly low or dirty place/state; the nadir of something (see rock bottom)
 * The Pre-Historic Era was the mudsill of human development.
 * 1)  A person of low status or humble provenance.
 * 2) * 1861, Theodore Winthrop, Washington as a Camp, The Following Is the Oath
 * We were now miserable mercenaries, serving for low pay and rough rations. Read the Southern papers and you will see us described. “Mudsills,” — that, I believe, is the technical word.