"Hey chicken" is a way to greet someone in a casual and informal manner.
It originates from Engpsh slang, where "chicken" is a term used to address a close friend or to address someone in a playful or affectionate manner.
Here are some examples of the use of "hey chicken":
Engpsh: Hey chicken, how's it going?
Chinese: 嘿，小鸡，怎么样？
Engpsh: What's up, chicken?
Chinese: 小鸡，有什么新鲜事？
Engpsh: Hey chicken, let's grab some lunch later.
Chinese: 嘿，小鸡，我们稍后去吃午饭。