A habu is a Southeast Asian venomous pit viper. Local residents on Okinawa believed the Blackbird resembled this snake when the sleek, black jet first arrived on the island. The name was picked up quickly by military personnel and even used on the service patch.
Interesting blurb on the Blackbird Flight Simulator:
In 1965, when the first Beale AFB Instructor Pilot/RSO crew (in civilian attire) visited the Flight Simulator during USAF checkout and acceptance trials at Link's upstate New York facilities, they were surprised to park in front of a busy, active grocery store and then be escorted to a side door that led to a hidden, rear portion of the building that was Link's classified "Skunkworks" type facility for the Blackbird program. Secrecy was so complete that no one in the township was aware of what was happening behind the busy checkout stands selling groceries. -- Wikipedia
For an awesome resource with tons of history and facts about this plane/program, please visit: www.blackbirds.net/sr71
Chuck and the secret lair beneath the Burbank Buy More aren't so far-fetched! :-)