A glance at the written heritage of Iran reveals that Iranians have always referred to Arabs using the word “Tazi” or “Tazis” and referred to Arabic using the word “Tazi” language. However, it is not quite clear why and since when they have called
Arabs as “Tazis”, or why the definitions of this word and the reasons given for such a denomination are so different and sometimes contradictory in various Persian and Arabic sources. Here, following a document analysis method, the author intends to examine the etymology of this original Persian word and the reasons behind its application to Arabs in various historical and religious texts and dictionaries. The findings of the study indicate the presence of a mythical and religious belief among ancient Iranians stating that “Taz” was the great ancestor of Arabs, and that is why the word “Tazi” is applied to Arabs themselves and their language.