The word poppycock doesn't have anything to do with plants or chickens at all. Today meaning "nonsense" and kind of archaic, the word comes to us from Dutch pappekak, which literally meant "doll excrement", a portmanteau of pappe, "food", and kak, "dung". Pappe, which described softer foods given to youngsters and (a cousin to the English word pap, also meaning "baby's food") is connected to a "doll" meaning through the connection of an infant. There are several languages which use sort of a papa sound to describe babies eating, and it's suspective that this is imitative of child-directed speech. Meanwhile, kak came from the Latin word cacere, a verb for "excretion", which in turn derives from the reconstructed Proto-Indo-European root kakka, bluntly meaning "to poop". Anyway, accusing someone of being poppycock is actually the equivalent of telling them to eat their own dung.
Adam Aleksic, a freshman studying linguistics at Harvard University, has been described as the internet's sixth most famous etymologist. He has disturbing interests in words, vexillology, geography, board games, limericks, and law, and he loves writing about himself in the third person.
The Etymology Nerd