The polemical anti-Christian narrative Toledot Yeshu (henceforth, TY) is the earliest freestanding composition written by Jews against central tenets of Christianity. Broadly speaking, the narrative is a subversive rendering of central aspects of the life of Jesus and was composed at some point during Late Antiquity or the early Islamic period. This article discusses the origins of the long ("Helene") version of this polemical parody, which was well known in most parts of the Jewish world, and argues that this expanded version of the narrative was a creation of the classical Islamic period, in Judeo-Arabic, likely around the ninth or tenth century. This argument is supported by manuscript evidence in Judeo-Arabic from a slightly later period. Furthermore, Jewish-Christian debate in a variety of Near Eastern languages was and remained active during the first few centuries of the Islamic period, and the tone and contents of TY are typical of the polemics composed during this time. A further backdrop for the creation of this Jewish polemical narrative was the existence of numerous accounts of Jesus's birth and childhood in Arabic, among Muslims and Christians, which would have provided fertile ground for the creation of a Jewish account of Jesus's birth and childhood, or "Jewish infancy gospel," as found in TY.