The word Mahout originated from the Hindi words Mahaut and Mahavat that describes the family profession of keeping and riding elephants. Usually a boy will be assigned an elephant early in his life and will be bonded throughout their lives (http://en.wikipedia.org/wiki/Mahout).
At an elephant conservation park in Chiangmai, Thailand, I learnt that each elephant was assigned to 3 mahouts to be cared for. The reason was that the elephant remembers his caregiver very well and gets attached to him. If only one mahout was assigned and he had to leave for some days, the elephant may miss him and choose not to eat or cooperate with the other mahouts. Some of them fell ill from missing their personal mahout. So to keep them from having to go through such emotional strains, they rotate the mahouts amongst the elephants so that they will be familiar with at least 3 of them. These mahouts would then be able to take leave or go back to their hometown without worry.
The mahouts originate from Myanmar (formerly known as Burma) and all the mahouts in this camp were from Myanmar. Historically, the elephants came from Burma and were cared for by the mahouts in that region and that explains why the mahouts had come from Myanmar where they still train their people to become mahouts and have been a tradition passed down from generation to generation. We were also told that mahouts spend all their waking hours with the elephants and were able to communicate with them in a special way that no one else could. They understand the elephants like their own siblings or children and were able to bond with them and live amongst them like a part of the elephant community. Likewise, the mahouts could not spend too long a time away from the elephants and would miss them too. They seemed happiest when they are with the elephants.