"We are big, you are small."
And I believe those words were deliberately chosen in order to go against a general tendency in languages for words meaning "large" to have a vowel pronounced with your mouth wide open (e.g. "ah") and words meaning "little" to have a vowel pronounced with your mouth closed (e.g. "i" or "u").
Instead, Klingon has mach with an open vowel and tIn with a closed vowel.
(On the other hand, the English synonyms "big" and "small" are also counterexamples -- it's just a tendency, after all, not a rule.)