When I was younger, I quite naturally watched Atlantis: The Lost Empire and was struck by the term Kida uses a bit before 1:30 in the opening (Matim for mother, pronounced mah-tim).
I’ve never personally called my mother Matim, though I use it as mental shorthand and keep it to myself. I also did something that made a whole lot of sense to kid-me; I just swapped out the m for an f in order to have a word for father – Fatim (pronounced similarly, fah-tim).
With this line of thinking, it made perfect sense to mentally refer to Fenrir as Fatim. Then I decided to see if it actually meant something (in case I was leading others to an incorrect meaning). I’m not sure how much Fatim is used as a name, but Fatima is an Arabic name with a meaning (according to this) of “to abstain”. There are variations in spelling, and I’m pretty sure it’s pronunciation differs from what I use (though the written form doesn’t necessarily reflect this as well as spoken formatting).
Abstaining ties into self-control, and this has a new godfeels level of fitting.