I have never understand why people use the word "chicken" to describe cowardly behavior. I have spent enough time at farmed animal sanctuaries (and at chicken farms as a child) to know that if you were ever cross a rooster and he doesn't want you there, he will let you know and will persuade you to leave in no uncertain terms. Likewise, you don't want to try and get between a hen and her babies. Just call a coward and leave chickens out of it.
Meme, Chicken, Coward, Hen, Rooster