User blog comment:XD1/Season 4 Live Chat/@comment-70.215.65.4-20131019135332/@comment-196.221.68.145-20131029105134

When Grace was a baby her first try to pronounce her father's name ended up with her saying "danno" instead of "Danny" or "Dad". He liked that & kept it as a secret name between the two of them (Guess the story was told in S1 E1 or 2).