See Sh. Friedman, MAARAV 21(2014[2017]) p. 314 and now his "Elucidating Talmudic suryaqe—an Exercise in Talmudic Lexicography", pp. 383-408 in Hakol Kol Yaakov: The Joel Roth Jubilee Volume, ed. Robert A. Harris and Jonathan S. Milgram, where a convincing argument is made that the original talmudic meaning is not "streak" nor "vein", but simply "tiny strand, trace". The "heat or glare of the Sun" cited by BarBahlul for Syriac ܫܘܪܝܩܐ is clearly an Arabism from the common Arabic root for sunrise, east and has here been omitted. We assume that the correct Aramaic root is indeed srq, "to comb fabric".