Mine have a whole vocabulary of sounds--they cluck, chirp, trill and when they are stalking a fly and it's too high to reach, they open their mouths and make this semi-silent clicking/meowing noise. I think they are swearing because they can't reach the darn thing. LOL
We have 3 Siamese, who are by nature very vocal...but none of them sounds like Keemo. She also "swears" when she can't reach something, and often makes the same sound when she is getting ready to do something that she isn't supposed to. Such a funny little cat!