Things that go up must eventually return to the earth due to gravity.

Things that are launched into the air will return back down to the ground. Why? Because gravity, that's why. Whether it's someone jumping up as high as they possibly can, a football being thrown over an open field, or planes flying from place to place, these things can't remain off the ground forever; eventually, due to the force of gravity, they will come back down. Hence, this phrase looks like it came from a basic observation of what gravity does to people or objects.

This idiom was being used at least as far back as the 1800s and its wording is identical to what we say today. For example, the saying makes an appearance in Theodore Sedgwick's Hints to my Countrymen. 1826:

" When one boy among a dozen throws a stone into the air, crying out, that 'what goes up must come

down,' it is very likely so to happen. "

* Barnes' pet bird escaped from his house and flew away. He figured that what goes up must come down. so he put a perch outside and hoped his pet bird would land on it and return home.

Note: A phrase's origins are, a lot of the time, very uncertain. The origins you see listed are the more plausible theories that are floating around for how or where an expression came to be, but just remember, theories are not always fully accurate! The quotes which have the phrase in them are the oldest written forms of the phrase I could find, but thre's always a chance of an older recording being out there. Perhaps I've missed it. Feel free to let me know if you know of any!

Also, remember that just because you see an idiom in some old book or newspaper, let's say they're from the year 1893, well it doesn't mean the saying originates from that source. In all likelihood, if an expression is already in use in a book or newspaper, then it's probably older. Nevertheless, these old quotes serve as a way to show the reader how far back in history some of these sayings go, which can be quite interesting!