Here
http://www.reliance.com/mtr/pwrspy.htm
it says
Two phase power supply is found in only a few scattered areas around the U.S. and the world. Two phase motors are not generally available in stock; Check AC Products in Cleveland for availability. Two winding multi-speed motors are difficult to wind for two phases, therefore, transformation to allow three phase operation is recommended.

There is no special term mentioned for this system, nor for 3-phase supply. If you split a 2-phase supply, you would indeed get half the voltage.