The language of High Cromlech, popularly known as Deadish.
"The sounds of Quiesy were formed in the back of the throat, softly barked, the noises swallowed, and interspersed with precisely timed silences as important as the sounds. ... Many of the thanati gentry had sewn-shut mouths ... and others had voiceboxes too rotted to work. There were modes of Quiesy spoken with hands and eyes, as well as written forms."