Belldandy and her sisters are based on the Norns, who were the goddesses of fate in Norse mythology. Belldandy (Verthandi) was the goddess of the present. Urd (Urthr, Urdr) controlled the past, and Skuld represented the future. They lived at the base of Yggdrasil, the World Tree. In the original "Aa! Megamisama!" manga, the computer system used by the goddesses is also named Yggdrasil.
Kikuko Inoue actually did most of Belldandy's voice work, actually voicing about a dozen of the 48 shorts in the Mini-Goddess series, as well as Belldandy herself in both the OAV and the TV series.