The answer is egg, because egg-laying creatures predate the chicken.
If we count it as a chicken egg only, then it depends on if you describe a chicken egg as "an egg laid by a chicken" or "an egg that could hatch into a chicken".
The answer is egg, because egg-laying creatures predate the chicken.
If we count it as a chicken egg only, then it depends on if you describe a chicken egg as "an egg laid by a chicken" or "an egg that could hatch into a chicken".