Shang Xian, if I have a good relationship with boys and girls, it may be a coquetry for boys to call girls "brats" in daily life. I think girls are as innocent and pure as children, so I will call them "wet behind the ears". However, if a boy calls a girl "wet behind the ears" in a provocative way, he may think that the other person behaves like a child. If this move makes girls unhappy, I suggest that boys don't call girls "wet behind the ears" like this.
However, using a gun is a kind and lovely nickname on the internet now. Many times it means that the person being called is cute and gives people a better feeling, so people prefer to call each other a kid. This nickname means coquetry.
It should be noted that different nicknames have different meanings on different occasions. I also hope that when addressing others, I can greet them with appropriate and reasonable addresses, which is also conducive to the feelings between two people and can better reflect my own quality and education.