For pretty much all real smaller languages the alphabet and writing concepts was a mishmash of other, more developed languages that their educated people happened to know. And usually the early versions were horrible, horrible mismatches trying to fit a square peg into a round hole; multiple sounds mapping to a single 'proper' letter, making up new symbols, making up new writing concepts to represent peculiarities of grammar (and then finding out that these concepts don't really work).
There are languages that have tried multiple very different scripts - depending on time period, latin, cyrillic and arabic-style; with different writing styles of the exact same spoken language having almost nothing in common if they were developed in isolation because of differences in location&country.
Would Korean fall under this category along with Vietnamese?
I ask because while I can't read Korean, I know enough to sound things out based on its character set. Which is really really cool.
I also dated a vietnamese girl and the latin script they use now instead of the hanji/chinese derived script in use prior is so pervasive almost nobody can read older vietnamese outside of scholars.
There are languages that have tried multiple very different scripts - depending on time period, latin, cyrillic and arabic-style; with different writing styles of the exact same spoken language having almost nothing in common if they were developed in isolation because of differences in location&country.