Yes the long S [1]. Not used at the end of a word. It's the origin of the German ẞ, which is visually a long S with a short s after. Increasingly often just written as ss, with some German dialects officially doing away with ß. Words like "possess" in English used to be written pretty much (visually) like poßeß or poſſeſs.
It's also the origin of the integral sign! (Mentioned on the Wikipedia article.) There's a nice accidental parallel between sigma notation (the discrete, "angular" summation) and integral notation (the continuous, "smooth" summation).
Another s fact is that Greek has lower case σ and additionally the variant ς that only appears at the ends of words, which is very Latin-s-like. https://en.wikipedia.org/wiki/Sigma
That shouldn't be too surprising. The technology used deeply influences writing. In the Latin alphabet, the upper case forms developed from the forms of letters used in stone and metal, with monumental carvings. While lowercase evolved from the kind of writing done with pen or brush on parchment or papyrus. Unsurprisingly, there are a lot more straight lines amenable to carving into stone in the upper case letters.
As I understand it, printed f and long S looked very much alike, and the usual tweaks in handwriting to make it clear weren't really easy in print. So they just dropped it altogether. One less letter required in the typeface, too.
The origins of the Latin alphabet are interesting too: miners in Egypt who didn't want to learn all the hieroglyphics decided to start using some of them phonetically, creating an alphabet
True classical latin didn't have lower case. Initial letters were written marginally larger, but what we'd now (mostly) think of as uppercase is what all the letters looked like.
> with glyphs that resemble uppercase letters (capitals) but reduced in height and weight close to the surrounding lowercase letters or text figures.[1] T
Wouldn't be the only one: The English thorn Þ character (making the "th" sound) was replaced by either the "y" character ("ye olde shoppe" was pronounced "the") or the digraph "th" based on a French mispronunciation (A really fast "tuh-huh" is pretty similar to the "th" sound) for use on printing presses made for countries without it.
