ghItlhpu' Quvar, jatlh:
I've just been asked this by a beginner. I know what I could answer, but I wondered if there is a canon explanation, and also what your answers might be. It has certainly been asked before: Why is it {tlhIngan maH} and not {tlhInganpu' maH}?
I don't think there's a canon explanation, but slogans tend to work better when they're more concise (Australia's political landscape is now at a point where the term "three word slogan" has become a term of political mockery), and no doubt Klingons think that way too. While tlhInganpu' maH is also in principle fine for "we are Klingons" - for a canon instance, note wo' tay' tlhInganpu' maH "we are UK Klingons!" (Radio Times) - I imagine it's just that the chant-like nature of the phrase lends itself to maximum brevity. QeS 'utlh