CO2 & COZ

The reason was because it was written in manuscript. So when they write CO2 in manuscript, we couldn't understand whether it's 'COZ' or carbon dioxide. So in order to evade confusing the description, they started writing as CO₂. Time goes by now is the age of the Internet, there're scarce manuscripts that is written as CO₂. Now nobody confuses CO2 and COZ anymore.
COZ is a colloquial form of 'because'. --Ancient Greek Philosophers -18c Enlightenment Thinkers -Slashdotters