Genuflection has its roots in western Frankish customs and originally was how one greeted their superiour or Lord according to Sallic Law. One would get either one one or both knees, hold their hands out together un the traditional western manner see link http://www.princeton.edu/~puge/Praying%20Hands.gif
and bow his head on his chest.
The Lord would then clasp his hands around the submitting party as a sign of acceptance. Although, there are slight signs of similar things in the east, it is largely of a western mediaevel origin, where the bowing (and prostrating has a historical prominence in the Mediterranean.