My daughter has a nickname and I thought I'd explain how it became an addition to our family vocabulary.
Wonderful Husband would enter the house after a hard day of work and say, "Hi Sweetie! How was your day?" It became a bit confusing to him when both daughter and I would respond to his question at the same time. So one day he said to our daughter, "I was talking to your mom. I'm going to start calling you Young Sweetie so it won't be confusing."
Without missing a beat our daughter said, "Oh, so I'll be Young Sweetie and you'll call Mom Old Sweetie."
Now you have to understand that Wonderful Husband knows that isn't a great idea (after all we've been married for 27 years...so far) and started back-pedaling saying, "No, I'd never call your mom Old Sweetie. I'll call her Young Sweetie and I'll call you Younger Sweetie."
Too late. Every time Wonderful Husband calls her Young Sweetie, she'll pipe up with, "Aren't you going to ask Old Sweetie how her day was?" He'll say..."I've never called her Old Sweetie." Young Sweetie will come back with, "Oh yes you're the one who started calling me Young Sweetie," and with a twinkle in her eye she'll continue with, "and that's why you started calling Mom Old Sweetie."
Poor Wonderful Husband...he can't win this one! Ha!