An Etymological Dictionary of Astronomy and Astrophysics

A substance, such as mud or dust, that soils someone or something (OxfordDictionaries.com)

Etymology (EN): Metathesis of M.E. drit, drytt “mud, dirt, dung,” from O.N. drit, cognate with O.E. dritan.

Etymology (PE): Cerk “dirt, filth.”