N is for...

N is for Naihanchi/Neh Boo Jin

Neh Boo Jin translates to 'Inward Step Advance' and is the original name for the Naihanchi forms.  While the exact origin of these forms is unknown they are believed to have originated during the Song dynasty in China around 900 years ago and then brought through Okinawa.  Originally one large form it was split up into three separate parts for teaching purposes.  A diagram of the first of the three can be seen below.

Source

The first thing you probably notice about the forms is that unlike the others they are all done on one line with no turns.  The reason for this is that the forms were developed as a defense against 4 to 8 opponents with the performer pinned against a wall.  This linear movement encourages the student to focus on refining hip movement to deliver power without the forward momentum of the body to help.

The second thing you probably notice is that you spend most of your time in these forms in horseback stance which is why it is referred to as the "Iron Horse" form.  Iron because the movements are meant to be incredibly strong and powerful (this is not a graceful form, it's a hard-hitting one) and horse because of the stance.

Like Kong Sang Koon, the Naihanchi forms can be seen in most styles of martial arts due to their lineage- China through Okinawa into Korea.