It's semantics! The chicken evolved from something (I'm going to call that something "Chicken Prime"). One day a Chicken Prime laid an egg and then out came a chicken from the egg.
So would the egg that the Chicken Prime laid be considered a chicken egg? Or because the Chicken Prime was the one who laid the egg, would the egg be considered a Chicken Prime Egg?
I'll give credit to the egg layer and say it was a Chicken Prime Egg; the chicken came first!