The word “Yubaba” comes from several places. Firstly, it is a reference to the Japanese word “Onibaba,” referring to a demonic woman. It’s also derived from Baba Yaga, a witch-like being who lives in a walking house, a figure who finds her origins in Slavic folklore. Incidentally, Baba Yaga’s moving house was also featured in Miyazaki’s film “Howl’s Moving Castle.”
Thirdly, it is a reference to Yama-uba, a yokai (shapeshifter) from Shinto folklore. Yama-uba take many forms, and tend to lure people into ghostly dimensions to perform their own kamikakushi. Notably, in certain areas of Japan, a yama-uba is an old woman called a kawajoro, a wailing banshee who complains that a local dam is about to burst, and that a river is about to wash away her home. This is significant as Yubaba has enslaved Haku, controlling a river. “Spirited Away” is a drama of a yama-uba trying to control the river that would wash her away.
Yama-uba aren’t wicked, necessarily. In many folkloric stories, yama-uba care for their children deeply, which is reflected in the way Yubaba spoils her creepy, outsize baby. Yama-uba’s children are called yamawaro.