Clauson (1972)
An etimological dictionary of pre-thirteenth-century Turkish
p. 474
tokku:z
(d-) ‘nine’. There is no doubt that this word and some other numerals originally had a medial double consonant, see Clauson, ‘The Turkish Numerals’, JRAS, 1959, p. 20, and this double consonant would not have been written in the Runic or Uyğ. scripts. It survives at any rate in SC Uzb. tükkiz; SW Az. doğğuz and Çuv. taxxar, as well as taxar Ash. XV 7, 11. The initial d- survives in SW Az., Osm., Tkm. A l.-w. in Pe. and other languages, see Doerfer II 976. Türkü viii tokuz I N 6, 9: viii ff. toku:z IrkB 55, 60: Yen. tokuz Mal. 30, 2; 32, 10: Uyğ. viii tokuz Şu. E 3: viii ff. Bud., Civ. tokuz is fairly common: O. Kır. ix ff. tokuz Mal. 23, 1; 51, 2; toku:z do. 45, 2: Xak. xi toku:z Kaş. I 437 (tokso:n); III 127, 14; n.m.e.: xiii(?) Tef. tokuz 309: xiv Muh. tis‘a dokuz Mel. 81, 8; toku:z Rif. 186: Çağ. xv ff. tokuz ‘adad-i nuh, in Ar. tis‘a San. 181r. 9; in do. 20v. 15 mentioned as one of the numerals spelt alternatively ba-tašdīd or ba-taxfīf, i.e. as tokkuz or tokuz: Kom. xiv toğuz CCG; Gr.: Kıp. xiii tis‘a tokuz Hou. 22, 7: xiv ditto İd. 65; tokkuz (sic) Bul. 12, 12: xv tokuz Kav. 5, 1 a.o.o.; takuz (sic, in error) Tuh. 60b. 8.