Steven Pinker on Friendship

"To a linguist, the phenomenon is familiar: the euphemism treadmill. People invent new "polite" words to refer to emotionally laden or distasteful things, but the euphemism becomes tainted by association and the new one that must be found acquires its own negative connotations. "Water closet" becomes "toilet" , which becomes "bathroom," which becomes "rest room," which becomes "lavatory." … The euphemism treadmill shows that concepts, not words, are in charge. Give a concept a new name, and the name becomes colored by the concept; the concept does not become freshened by the name."