We can give credit to Grandmaster Choi, Yong-Sool for many of the principles and techniques taught in HapKido. Many of these priciples can be traced back to his study in Daito-Ryu Aiki Jutsu. It is also believed that the name HapKiDo was first used by GM Choi and GM Ji.
The popularity of the name HapKiDo can be creditied to both Grandmaster Ji, Han Jae and the late Han, Bong Soo who studied under GM Choi.
GM Ji throwing Master Janisse
Hap Ki Do
The common translation is:
"Way of coordinated power".
What does this mean to the martial artist? Is it to push when pulled or pull when pushed? Is it to use your opponents energy and redirect it? Is it to use the movement of your body to transmit maximum power with minimum effort?
If you answered yes to any of the above, you are correct and on your way to becoming a master in about 20 years.