What is the origin of the name 'Sai Baba' as explained in the introductory chapter?

The introduction in Chapter 0 explains that the name 'Sai Baba' was given to Maharaj upon his arrival in Shirdi. When he, dressed in a kafni, cap, and dhoti, entered the Khandoba temple, a resident named Mhalasapati greeted him with the words "Aavo Sai Baba," which translates to "Come, Sai Baba." Maharaj adopted this name and was known by it for the rest of his life. The text highlights this by mentioning that when his testimony was taken in a commission and he was asked his name, he replied, "They call me Sai Baba."