When I was a little girl, my mother told me that work horses, like Clydesdales, were called Big Brother Ponies. Not knowing that she just made this up, based on My Little Ponies, I referred to these horses as Big Brother Ponies until I was in my early 20s.
Luckily the didn’t appear in conversation much. However, a friend gave me a weird, confused look when I mentioned a draft horse one day. “You know, a Big Brother Pony?” She said, “No, I’ve never heard of that.”
Of course, when I called my mom she told me, “Oh yeah I just made that name up” and laughed.