How do you explain the presence of non-Arabic names in the Holy Quran despite Allah Almighty's saying: "Indeed, We have sent it down as an Arabic Quran that you may understand"?

Scholars have differed regarding whether there are words in the Holy Qur’an, other than proper nouns, that are not of Arabic origin. Some have maintained that there are no such words in it, and that the Qur’an is purely Arabic, and that any words found therein which are attributed to other languages are merely instances where languages converged. Others have maintained that such words do exist in it, but that their scarcity does not preclude the Qur’an from being a clear Arabic scripture.