It’s how you write “d’or” in Japanese
Surely, if you were going to call it d’or you’d call it, you know, d’or, not (instead of using 金) borrow the French d’or translate that the katakana, then bastardise the borrowed French back into (not) English.
Don’t get me wrong that deore doesn’t mean deer, fine, I get that, but your explanation is not the more plausible one of the two.
Also starion being stallion sounds awfully like it’s a racist urban myth based around the stereotypical pronunciation of “r” by the Japanese. You might be right but it’s a bit too *snigger snigger* to sit quite right.
(as an aside, isn’t ィ in your katakana superfluous and making it read deiore? Isn’t it デオーレ? I’ve not done any of this in about 20+ years mind so happy to be wrong)