We learned the word bear (der ber / דער בער) pretty early on in class. We also learned the plural of bear (di bern / די בערן). That's when I got this idea...
So, because I'm a pain in the tuchus, I asked my teacher how to say bull. Der bik (דער ביק) is the word for bull in Yiddish. I think our Yiddish teacher said the plural of bik is di bikn or di bikhn (bottom picture). It could also be spelled די ביכן. I'm not sure.
I've been looking around the internet though, and one dictionary said the plural form of bik is bikhes, so that is what is shown in the top picture.