Clauson (1972)
An etimological dictionary of pre-thirteenth-century Turkish
p. 48
D ıḏukluk
Hap. leg.; A.N. (Conc. N.) fr. ıḏuk. Türkü viii ff. (a cow . . . gave birth to a white dappled bull-calf) ıḏuklu:k yara:ğay ‘it will be suitable as (an animal for) dedication to heaven’ IrkB 41.