This is an insult in English, but it might not be in Vietnamese. Does anyone know? I think calling someone a chicken in Vietnamese isn't an insult like in English.
In Vietnam call someone is pig and chick to be impolite. I think in this situation it may say about the name of the birth's year. Vietnam and China take twelve animals to call years. Sometimes we say "you are a pig" instead "you are your birth's year of the pig".
It's an insult to call someone a pig, but calling someone a chicken doesn't mean anything