The original Hawaiian poi dog derived its name from poi, a Hawaiian staple food made from kalo or taro root. Poi was used to fatten the dogs for use as food because meat was too valuable to be used as dog food. Since the Hawaiian Islands did not have large land mammals other than feral hogs, Poi dogs weren't needed for hunting. The dogs were never deliberately bred to a standard, but human and natural selection still came into play.
European explorers like Captain Cook encountered pot-bellied, short-legged poi dogs that freely associated with hogs in the village. The dogs had very short hair that could come in any color, but brown poi dogs were regarded as distinct enough to warrant a specific name. The dogs also had peculiarly flattened heads. The latter trait is sometimes ascribed to the diet of the dogs in some unspecified way. Considering that poi does not require chewing, the dogs might have lost the need to maintain strong temporalis muscles; a reduced temporal fossa will cause a dog's head to appear flattened. Poi dogs were considered rather dim-witted and sluggish – any good hunting dog with acute senses would neither make a good poi dog, nor be particularly useful on the islands – however, the dogs were strong-willed and not easily commanded.
The poi dog was a two-purpose breed – used for food and as a lucky charm. Unsuited for anything else, the breed declined to extinction as the native religion was abandoned and eating dog meat became unfashionable. Feraldogs of European settlers interbred with the poi dogs, and by the early 20th century at latest, the breed disappeared as a distinct entity.
Today, the term "poi dog" is most often used to refer to mix-breed dogs, but also attribute specific characteristics to Poi dogs, including the ability to eat anything, a strong will, and a unique appearance composed of different breeds. "Poi Dog" is also used to describe mixed breed dogs; sometimes, the term is colloquially used to describe people of mixed Hawaiian-Anglo heritage, although the more common term in use is hapa.