The code for successful surprise (and the movie's title) "Tora! Tora! Tora!" was a shortening of the words totsugeki (attack) and raigeki (the Japanese term for torpedo bombers), and was originally spelled "To ra, to ra, to ra!" Those two shortened words were interpreted by American radio operators, who happened to intercept them, as the Japanese word for "tiger"; hence "Tora! Tora! Tora!"
The crash landing of the B17 was real. During the filming, one of the bombers could not lower its right landing gear due to a broken jackscrew, so the producers rushed a crew to the airport to film the bomber's crash landing. They foamed the edge of the runway, and foamed another pilot's back with a hooded raincoat on while sitting on the edge of the runway. He called elevations to the pilot in the plane, and everything went OK until the wingtip hit a runway light which spun the airplane around.