You are right: Leib, Loeb and Loew (often with O Umlaut) are Yiddish forms of ARI ("lion"). It may well be that the Greek word "leon" was imported from the east and can be found in the Hebrew word "levi" ("lion"; spelt with the letter Beta) and "lavi" ("lioness"). The name LEVI is spelt with a Wav (Vav?), as far as I know it was traditionally given to descendants of the Levites (I'm not sure about this).
Another German name may have influenced those names you mention: Lieb ("dear")like in names as Liebwin/Levin.