This is a cool article I originally saw a year or two ago. Mental Floss breaks down “12 Letters That Didn’t Make the Alphabet”.
The first example is one you’ve probably seen before:
Have you ever seen a place that calls itself “ye olde whatever”? As it happens, that’s not a “y”, or, at least, it wasn’t supposed to be. Originally, it was an entirely different letter called thorn, which derived from the Old English runic alphabet, Futhark.
Thorn, which was pronounced exactly like the “th” in its name, is actually still around today in Icelandic. We replaced it with “th” over time—thorn fell out of use because Gothic-style scripting made the letters y and thorn look practically identical. And, since French printing presses didn’t have thorn anyway, it just became common to replace it with a y. Hence naming things like, “Ye Olde Magazine of Interesting Facts” (just as an example, of course)
Oh, and if you’ve ever wondered about the origin of the ampersand (“&”), look no further:
Today we just use it for stylistic purposes (and when we’ve run out of space in a text message or tweet), but the ampersand has had a long and storied history in English, and was actually frequently included as a 27th letter of the alphabet as recently as the 19th century.
In fact, it’s because of its placement in the alphabet that it gets its name. Originally, the character was simply called “and” or sometimes “et” (from the Latin word for and, which the ampersand is usually stylistically meant to resemble). However, when teaching children the alphabet, the & was often placed at the end, after Z, and recited as “and per se and,” meaning “and in and of itself” or “and standing on its own.”
So you’d have “w, x, y, z, and, per se, and.” Over time, the last bit morphed into “ampersand,” and it stuck even after we quit teaching it as part of the alphabet.
The rest of the article is really interesting too, so I recommend you go and read it.