Quieten comes from quiet + -en; quiet from Old French quiet, from Latin quietus ('at rest, calm'), past participle of quiescere ('to rest'), from quies ('rest'). The suffix is part of the word's derivational shape, marking the final grammatical or semantic role while the base supplies the central meaning. As a verb, it means "to make or become quiet or calm", so the modern sense keeps the older action or relation visible. Relevant historical forms include Latin quietus, Latin quies, and Proto-Indo-European *kʷyeh₁-. Derivative forms include quietening; related words include quiet, quietness, quietude, quietly.