Rebbe Yid:
First, the Rambam himself was Moshe, not Moussa or some other language-equivalent.
As well, “Aryeh” is mentioned in the Torah (Gur Aryeh Yehuda…)
You’re also ignoring the language issue: Aryeh is Lashon HaKodesh while Leib and Lionel and whatever else are not.