What is the origin story of the name 'Sai Baba' as explained in the Satcharitra's introduction?

The name 'Sai Baba' was spontaneously given to Maharaj upon his first appearance in the Khandoba temple in Shirdi. As Chapter 0 details, when he entered the temple wearing a kafni and cap, a devotee named Mhalasapati saw him and welcomed him with the words 'Aavo Sai Baba,' meaning 'Come, Sai Baba.' Maharaj accepted this greeting and held onto the name 'Sai Baba' until the end. Even when asked his name in a commission testimony, he replied, 'They call me Sai Baba.'