Disciple Kalyan's obedience for his Guru
Many disciples have attained spiritual progress by displaying complete obedience to their Guru. Kalyan Swami was one such disciple. His original name was Ambaji. Once, a branch of a tree had grown over a well. Samarth Ramdas Swami told Ambaji to chop off this branch. There was danger of falling into the well while cutting this branch. However, without fearing about it, Ambaji obeyed the Guru and started to chop off the branch with an axe. Ambaji was so engrossed with the thought of obeying his Guru that he forgot about the danger of falling into the well. Soon the branch snapped and he fell into the well. Everyone was terrified. Samarth Ramdas Swami rushed towards the well, peeped into it and shouted, “Ambaji, kalyan aahe na (Ambaji, hope you are well) ?” (kalyan means well-being in Marathi)
Ambaji replied, “Yes Swami, there is kalyan”
“Okay, then come up”, commanded Samarth. Ambaji climbed up the well and said that with Samarth's grace he was alright. From that day onwards everyone, including Samarth Ramdas started to call him by the name 'Kalyan'.
Reference : Sanatan's holy text 'Dosh ghalva ani gun jopasa (Part 2)'