Evolution is the key. The chicken only came into existence, after evolving from its initial form. At any time during that evolution, it would have had any number of forms, each deserving its own name. The final egg in the chain, before the chicken will have been from some other type of bird. Only the eggs after it became a chicken would count.

Evolution is the key. The chicken only came into existence, after evolving from its initial form. At any time during that evolution, it would have had any number of forms, each deserving its own name. The final egg in the chain, before the chicken will have been for some other type of bird. Only the eggs after it became a chicken would count.