The name 'Sai Baba' is globally recognized. Based on the introductory chapter, what is the specific origin story behind this name?

The introductory chapter of the Sai Satcharitra provides a clear account of how Maharaj received his famous name. After arriving in Shirdi with a wedding party, he entered the Khandoba temple. There, a devotee of Khandoba named Mhalasapati saw him and greeted him with the phrase "Aavo Sai Baba." As Chapter 0 explains, Maharaj adopted this name and it was used by most of his devotees. In fact, when his testimony was taken in a commission and he was asked his name, he replied, "They call me Sai Baba."