deaf as a post
Also, deaf as an adder. Unable to hear or to listen, as in Speak louder, Grandpa's deaf as a post. The first simile has its origin in John Palsgrave's Acolastus (1540): "How deaf an ear I intended to give him ... he were as good to tell his tale to a post." It has largely replaced deaf as an adder, alluding to an ancient belief that adders cannot hear; it is recorded in the Bible (Psalms 58:3-5).