The first vowel was long; this is independently supported by Turkmen gāz and Sakha xās. Chuvash xur shows the regular Oghur r corresponding to Common Turkic z, supporting reconstruction of the final consonant as *ŕ at the deeper Proto-Turkic level.
The deeper etymology is disputed.
Kāšγarī glosses qāz as “duck” and ördäk as “goose”; Clauson treats this as a reversal of the glosses in view of the broader Turkic evidence.