The word 'sky' has an interesting history! It comes from an Old Norse word 'ský', which means 'cloud'. Long ago, the word was used to describe the part of the atmosphere that we see above us, where clouds float and where the sun shines.
As people began to use the word more, it changed and evolved into 'sky' in the English language. Over the years, many variations of the word appeared in different languages, but they all relate to the same idea of the space we see above us.
So, you could say that the word 'sky' has been 'changed' by many people through history as languages transformed. But, there wasn't one specific person who changed it. Instead, lots of people over a long time made it what it is today!