They couldn't resist the pun.
http://en.wikipedia.org/wiki/KH-13

I always thought it was because DC is secretly in cahoots with Aloha Air Cargo Flight 13 Some say, it's his secret air fortress O_O

Ha-ha... keyhole.

that was great and probably true

I just thought it had to do with the 13 being Nomuras favourite number.  And the fact since we're only on KH2 right now it'd be a long time before people start getting it confused with one of the numbered releases.

It's really named kh13 because it's 

H13 

for hedgehogs

with a k slapped at the beginning

http://en.wikipedia.org/wiki/Key_Hole

Looks like KH13 is run by 4 DCh-norts named Corona

 

 

C O RONA

 

 

NOW I KNOW