Before being termed "Indian style", it was (and still is in some places) known as sitting tailors fashion. This was called such because tailors most commonly sat upon their work table to keep the fabric clean and provide a good workspace. That particular method of sitting supports the back muscles and puts an even curve in the spine, allowing one to sit for hours comfortably once used to it. In fact, the Sartorius muscle was named for tailors (sartorial/sartor) because it is so elongated in them. They also have enlarged blood vessels in the legs to prevent the legs from falling asleep as easily. Tailoring is one of the most ancient trades, so that term could go quite a long way back.