Punga in maori mythology is a supernatural being, the ancestor of sharks, lizards, rays and other deformed, ugly things, hence the saying "te aitanga a punga" meaning "the offspring of punga" used to describe an ugly person. this can be helpful when you want to insult someone without them knowing exactly what you mean, confusing them. It's really fun. it can also be shortened into just calling someone a punga, calling them ugly.
that girl must be the offspring of punga. (meaning -> that girl is ugly)