Wikipedia
In Māori mythology, Irawaru is the origin of the dog. He is the husband of Hinauri, the sister of Māui. Māui becomes annoyed with Irawaru and stretches out his limbs, turning him into a dog. In some stories, Irawaru as a dog eats faeces. When Hinauri asks Māui if he has seen her husband, Māui tells her to call “Moi! Moi!” whereupon the poor dog runs up, and Hinauri, learning the truth, throws herself into the sea (Tregear 1891:107).
Versions differ as to the cause of Māui's annoyance with his brother-in-law. In some, he is jealous of Irawaru's success at fishing; in others, he is angry at Irawaru's refusal to give him a cloak, or disgusted at Irawaru's greedy nature. In traditional Māori society, the relationship of brothers to their sisters was close, and many stories deal with the tension and rivalry between brothers-in-law. The story accounts for the characteristics of dogs: they share human homes and food, they respond to commands, but they also have some habits that people find disgusting (Tremewan 2002:95-96).