From Longman Dictionary of Contemporary Englishpet nameˌpet ˈname noun [countable] NAME OF A PERSONa special name you call someone who you like very much
Examples from the Corpus
pet name• Some Floozy Named Flo: he even had a pet name for her.• It's only a pet name for Henry.• He had never called her by her family pet name, Fifi, even when she lived at home.• Derwin has pet names for all his employees. 