~note on the etymology of Castiel~
Eric Kripke says that he got the name for Supernatural’s first angel character by googling “Angel of Thursday.” Because the show aired on Thursdays.
Nowhere lists “Castiel” (or anything close to Castiel) as the “angel of Thursday” but the influential 1994 kabbala/medieval grimoire mashup A Dictionary of Angels says the “Angel of Thursday” is Sachiel.
I am 99% sure that Kripke found this name, flipped the two consonants to get Cashiel (possibly testing the waters, not wanting to use the name of an actual angel case people got mad) then changed up the spelling slightly to make it easier to pronounce.
However, there is a historical angel named Cassiel. Not sure Kripke knew this.
Cassiel exists in both Islamic and Jewish traditions, so the name has about 40 different spellings and half of them start with Q. It also gets translated a bunch of ways - main ones are “speed of god” “anger of god” and (symbolically I guess) “fire of god.”
Anyway, my point is I think the Supernatural writers began identifying Castiel with specifically Cassiel. This would explain their really, really weird insistence on spelling Castiel’s nickname “Cass” instead of “Cas.” It also helps with translating the stuff Cas writes on Dean’s ribs. He sure seems to be referring to himself as “angel of fire.” [1]
Cassiel is also big character in famous German arthouse film Der Himmel über Berlin (English title: Wings of Desire) and its American remake City of Angels. Both of those films seem to have been pretty big influences on the way Supernatural angels look and work. And the character Cassiel is extremely torn between his angelic nature, and his love for humanity. So I guess the writers thought that was appropriate.
NOTE:
[1] https://supernatural-tv.livejournal.com/1991062.html. Translation of the Enochian. (It’s weird to say “translation” since Enochian is much more a code than a language, and is very, very silly.)












