How did they come up with the idea of the iconic hockey mask for Jason Voorhees? He didn't even wear that mask before Friday the 13th Part III. So how did the makers get this idea? As hockey mask didn't sound so scary before Jason wore it. Did they ever address this in any interview or anything?
Friday The 13th creator Sean S. Cunningham revealed that actually.
From this article,
I think Steve had done a whole bunch of hockey documentaries, when he was learning the editing craft, and I think that just out of that, he just said, ‘Let’s just try this,’ and that was the choice for ‘Friday 3’, and it just stuck
And every movie since then, there’s always, like, a readjusting of the mask, how to make it just right. But it has stuck, and the character himself has just morphed so dramatically over time that he has sort of, I don’t know… the movies wind up being about Jason, and not the people Jason is threatening.
You can also watch this in following interview of him.