Main reasons places develop their "local tongue" is by geography on who owns what or if that place is very isolated from others. If different places don't come in contact with each other they will have an independent growth and make their own language.

Slag is created and mainly used in a small group of people and it can develop a bond. Slang can be created from clipping(shortening a word), blending(combining words), and coinage(giving a word a new meaning). Usually it takes 30+ years for slang words to be added to the dictionary in 1950s, now it takes less than 10 years.

This article talks about how German language can be perceived as aggressive. Which it explains why we only see it as how it's pronounce instead of what it really means, because the pronunciation doesn't reflect the emotions of the words.

There are many different types of dyslexia that people can have either it is from reading, speaking, spelling or comprehending. This article talks about how certain types of dyslexia is shown and how people get it in the first place.