Being “The Etyman” comes from a desire to understand origins. The words we use didn’t just magically appear from nowhere but are the result of thousands of years of evolution. In the same way that people want to know where their families came from, etymologists want to know where words come from. By digging further and further back in time, we can work out the ulitmate source of a word. This is the word’s etymon.
So what’s the etymon of etymon? The Greek έτυμον means “true,” and this in turn lead to the Latin, etymon. We therefore use the word to refer to the “true” meaning of a word as it relates to its origin. It’s a synonym for the more common word, etymology, whose root is the same, but is typically used to refer to the process of finding a word’s origin.
You can use the adjective form of the word, etymonic, but only if you want to be seen as pretentious, snobbish, and conceited.