For some reason people are more comfortable swapping words when referring to the same thing. e.g. referring to a penis or vagina can make a person uncomfortable where using the words family jewels or down there does notMy guess is that something in the brain processes the sound, turns it into a meaning of some sought, the meaning is some how associated with the emotion and and object, but more closely associated with an emotion than and object hence using another word for the same object is more comfortable. My knowledge in this area is limited hence im askingdraw.io version of image https://drive.google.com/open?id=0Bz-acU90dFRMZ1ptQnl2SWJESWs 
How do euphemisms work in the brain?
cognitive psychology;brain