2. The pronunciation of "sauce" in Japanese is ちゃん, which is generally a nickname between very close people. For example, a Miao nationality is called Xinba.
The new "ちゃん" is also the name of the so-called X sauce. Good sisters will address each other like this. Boys will address close women, or they will use "sauce" when addressing their children. There is a feeling that the addressed person is very lovely.