Is it okay you use "pet name" to human in general?
Native speaker’s answer
Rebecca
"Pet names" are nicknames used to express fondness or familiarity with someone. We can use this word to refer to people, however, it is mostly used in reference to children or couples. In other situations, using the word "nickname" will be better. Ex: The couple has sickening pet names for each other. Ex: When I was a child, my pet name was Monkey.