Why was the term 'slang' made up? 'Slang' is just a messed up version of a word, what's the point in inventing it?

"Everything in nature is green and lively, or at least that's what we think. Most things we do hurt nature and make it the exact opposite, that's no way to treat a huge mass of life."

"Do you know the meaning of life? If you think you do you are probably right, everyone has a different perception of everything in life. So everyone, including YOU has their own meaning and way of life."