- The form assumes you have fallen to the ground and this is you trying to keep back an opponent until you can get up again
- The movement is a drop takedown
However I did recently think up an idea similar to the first option: what if it's a falling technique? The difference being that you can use the footwork prescribed in the form to get into the ground kick position. In fact, the collapse down onto one knee looks like the first part of an Aikido falling technique an instructor once showed me, in response to a strong shove that will take you to the ground. After searching online I found an example, shown in the gif below.
|Backroll setup vs Choong-Jang ground kick setup.|
Source: AikidoInstitute, Taekwondo-Mika
The rest of the set
What about the ground punch directly afterwards? Punching the opponent's groin? Actually, I prefer Paul O'Leary's explanation (which he details in this post) that it's a takedown. The back hand traps the opponent's instep while the "punch" pushes out on their knee, taking them to the ground. From here, still controlling your opponent's leg, you use the next two movements in the form -- clockwise step into side elbow strike followed by clockwise turn into closed fist guarding block -- to flip the opponent onto their stomach and possibly get a leg lock.
|An example of forcing the opponent onto their stomach with a clockwise turn. It's difficult to see, but the tori semi-circles around with his left leg, keeping his right leg in place. Source: Judoinfo.com/leglocks|
Edit 10-2-2018: I've reconsidered the drop takedown idea. If the flat spearhand thrust is used to push away the opponent's face while their right arm is pulled, that does put them off-balance which makes a drop takedown feasible. The roundhouse kick and knee push could then be used if the opponent slips free. But still, this could not have been the use of the drop in Woo-Nam, so I'm not totally certain why it's included.