Dag calls me his "little abacus".
As I read this, I thought you were going to say that is was because he could always count on you!

I dislike my wife's name pretty much, so I always call her "Darling." My problem comes when I need to introduce her, when I have to struggle to remember what her real name is! If I have to call her from another part of the house, I usually use the term, "You old bat!" which has become a standing joke, not least because it shocks/amuses visitors who don't know us very well.

My daughter and son, when very small, were known to us as "Poppy" and "Grolly." These days, they refer to me (but not to my face) as "the old man;" I can't complain, as this was the title bestowed on my dear father by my brothers and I.