In my family we have some ... jokes, I guess we can call them for lack of a better word. Or just reaction-sayings. If someone says X, we say Y. (X and Y are variables, not something we really say--except if someone says "Why?" we might very well say, "Because Y has a tail on it.")
Most of these sayings come from my dad. In passing them on to her children, my sister called them "Grandpa Lou-isms." Most of my dad's sayings come from radio programs and songs of the 1930s and 40s that he and his brothers heard in the barn. Out of context, they make no sense, but we say them anyway because that's how we were brought up.
One of these reaction-sayings is that if anyone mentions a bone, especially at the dinner table, my dad will say, "Save the bones for Henry Jones!" and all his brothers say the same. Sometimes my dad adds, "Cause Henry don't eat no meat," and, less often, a third line, "He's a vegetarian." I've heard that all my life and never thought much about where it came from.
Today I saw something online that was a list of song titles, and one was, "Save the bones for Henry Jones." So I googled it, and I found a video of Nat King Cole and Johnny Mercy singing that very song!
I thought, I wonder how many other of my dad's sayings are out there with some sort of background that helps them make sense? So I googled, "Spit in your shoe, give it to the teacher at half past two." That was something my dad said if anyone said, "What should I do?" But there was no sense to be found, at least via google. I found one or two mentions by people whose own parent said it, but never any explanation of why. (Because Y has a tail on it.)
But I did find this one. It so happens I like bananas, and if I ever said so, my dad said, "Because they have no bones." Voila.