The Shinkansen is known as the world's preeminent high-speed railway system. Its name emerged when the bullet train plans were being worked out.
The Railways Ministry decided to adopt a wider gauge of 1.435 meters, which has greater stability and can deal with greater traffic than the 1.067-meter narrow-gauge track that had been used even on trunk lines since the Meiji era (1868-1912). The project thus merited the name "Shinkansen," which literally means "new trunk line."
Source: Feb. 11, 2012, Yomiuri Shimbun morning edition