The baby is bitter in his heart, and the baby doesn't say what it is.

The baby is bitter but doesn't say it. Using the name "baby" is to claim that you have difficulties and grievances in your heart, but you don't say it, or you are embarrassed to say it, or you can't say it at all. There are many reasons, which may be afraid to say, don't want to say, and can't say. Fully expressed the feelings of self-mockery and injustice when encountering unpleasant things or being in a bad mood.