As babies and young'uns, my daughter was 'peanut' or 'monkey face'(her father's nick for her) and I called my son Sas-short for Sasquatch cuz he had such big feet. Later on, because he was so skinny, I alternated Sas with Chief Lackahiney. He kept the 'Chief' part for online stuff. His friend's dad said I should change it to 'Chumbo', but the son hated that. (supposedly that's more or less the same in spanish)
Now that they're teenagers, I just use the all-encompassing 'brat' or 'pain in my ass'.
