I perfectly now that.
I also know that the English language is more "supple", in many ways, than other languages, so that's why I'm wondering about "easer", even though it's not what's said in the song.
As far as I know, the word "easer" doesn't exist. It might possibly be used creatively for something that causes ease (just as someone who writes is a writer), but it's definitely not a substitute for "easier".
English is not so supple that you can randomly invent words and expect them to be understood, let alone accepted. In this case, there is no such word as "easer", other than as a possible noun that means "one who eases something."
The word has been used. I found a few examples by clicking on the links (dates) below the graph: "rupture-easer", and the technical terms "easer rail" and "easer section".
