Zum Ursprung des ø ~ y-Wechsels im Altuigurischen

Throughout all stages of Old Turkic, there has been a fluctuation between o and y- in word-initial position. This phenomenon has been previously explained as either a result of the diphthongization of the onset long vowels or as a reflex of an earlier *h-. The present study compiles all the words in the Old Uyghur corpus that exhibit the alternation of o ~ y-. In order to determine the cause of the fluctuation, cognates in modern Turkic languages are examined and their respective Early Common Turkic forms are reconstructed. The analysis reveals that not only does the vowel onset alternate with the secondary y-, but the primary y- also drops in a few instances. In most cases, the secondary y- results from the palatalization of the Common Turkic *h-. However, in very few cases, it is purely prothetic. The elision of the primary y- in Old Uyghur, on the other hand, is a distinctive feature of later Oghuz languages, particularly Azerbaijani, South Oghuz, and Khorasan Turkic. This suggests that the Oghuzic sound change in question may have already commenced in the prehistoric period. The replacement of the expected y- with h- in certain Khalaj words can also be attributed to this sound change.