Probably because it is from his movie "Return of the Dragon."
Royce by choke. I am a big, big fan of Bruce (he's probably the biggest sole reason why I even became interested in the Martial Arts). However, even he knew that he was dead in the water when it came to grapplers, which is why he started to train in Judo and Ju-Jitsu in hopes to integrate it into JKD.
It doesn't matter if you agree or disagree
... As long as I don't bore you and I spark a moment of thought, my goal is achieved
Queng leon queng tigre ecu tacacut, queca pa? - Pampangan Mandarigma Motto