When do you call pet names? I know many English names have their variants, nicknames or pet names. I wonder if given names or surnames or both may have their pet names? If both do, is there any difference between them, in meaning or affection ? Sometimes in movies children can be found calling their fathers petnames, what's the difference form calling them DAD? Is FATHER used as a dress ?Thank you, exparkpse. I meant Bill was a pet name while Willian was a common name,. as we know, Hillary call Clinton Bill.