Bosworth, C. E., and eds. P.J.Bear al.. “Yaylaq.” The Encyclopaedia of Islam, 2nd Ed., no. 11 (2002): 301–2.
This very short notice on the “summer quarters” of the old Turkic kaghans traces the etymology of the term to the yay of the Orkhon inscriptions, which means “summer”. As for Islamic times, examples are provided on the Ilkhans in Anatolia, and the Safavids in Persia.
CER: I-2.1-115