Work Text:
There are a few possibilities. Superficially, it seems to be one of these:
ש - ‘shin’ - as in ‘sh’
ע - ‘a’in’ - as in ‘a’ (a throat-deep sound). Also - means “eye”.
ך - 'chaf-sofit’ - as in ‘ch’ (sounds more like “hamster”, NOT “check” or “chamilion”), and is always at the end of a word.
ק - “kof” - as in ‘k’. And the most likely by meaning.
Although the ‘ק’ in the proposal obviously isn’t the same as the letter depicted in the series, It could be what was intended to be shown on screen. ‘Cain’ in Hebrew is written with this letter, and ‘mark’ in Hebrew, literally means “letter’ - ‘אות‘ means ‘letter’ AND ‘mark’ AND ‘sign’. It’s the same word. So, in the bible, it is written as follows (from Genesis ch.4 sentence no.15):
“וישם ה’ לקין אות לבלתי הכות אתו כל מוצאו”
Loose translation:
“and god put a mark (’letter’) on Cain, so that he won’t be hurt by anyone who finds him” (as in “seeks to hurt him”).
BUT.
IF you go and look at ancient Hebrew writing, you will find, that the most similar letter to the mark on Dean's arm is actually today's ‘ה’ (”he” as in “h”), which is the common and most used letter to signify the name of god ("The Essence Of GOD":
So, superficially, it’s one of the first ones I suggest. If you dig deeper - well, the last option seems most legit: Placing a letter that signifies GOD is much more probable than the first letter of the mark-carrier's - Cain’s - name.
Such a mark would bring great protection and would be recognized everywhere. So I bet it’s ‘ה’.