BĀGAYĀDIŠ (b-a-g-y-a-di-i-š, attested only in gen. °yādaiš/°y-a-d i-š), name of the seventh month (September-October) of the Old Persian calendar, mentioned in Darius I’s Behistun inscription 1.55 (see Kent, Old Persian, p. 161a). It is equivalent to Akkadian Tašrītu and Elamite Manšarki (several attestations only in the Persepolis tablets; see R. T. Hallock, Persepolis Fortification Tablets, Chicago, 1969, pp. 74, 724a). In the Persepolis tablets the Old Persian name is often rendered as Elamite Bakeyatiš (with numerous variants; see ibid., p. 673b), which indicates an Old Persian byform *Bāgayādya- (see W. Hinz, Neue Wege im Altpersischen, Wiesbaden, 1973, pp. 67f.). The etymological interpretation of the name Bāgayādiš is disputed: The form is best understood as “(month of) worship of the god” (perhaps Mithra), since bāga-yādi– “pertaining to *baga-yāda– “worship of the god(s)”” represents a common Indo-Iranian compound type (see J. Wackernagel and A. Debrunner, Altindische Grammatik II/2, Göttingen, 1954, p. 303, par. 190a). The interpretation of the name as “fertilizing the farmland” or “irrigation of the gardens” (thus W. B. Henning, JRAS, 1944, p. 134 = Selected Papers II, Acta Iranica 15, Tehran and Liège, 1977, p. 140), based only upon NPers. bāḡ “garden,” seems less probable.

See also baga.