Hey, I just watch the show. Sue me.
Well yeah, to people that wouldn't know "Kryptonite" from a hole in the wall. To those that know what it IS however, he uses the real term. To wit...
From Visitor:
Clark: No, it's called Kryptonite.
Pete: Kryptonite. Is that with a C or a K?
Clark: K.
From Onyx:
Clark: There was an accident at LuthorCorp, and I think that Lex was affected
by black kryptonite.
Martha: How did Lex get a hold of black kryptonite?
Clark: Well, I don't think he knows anything about the black K. I think he accidentally created it when he was experimenting with meteor rocks.
There were at least two other incidents of CLARK saying "Kryptonite" in Unsafe too. The only time that I can remember where he didn't say Kryptonite, referring to it as meteor rock (after he knew what to call it) was when he and Chloe were discussing the contract killer in Fade. It was necessary for plot, because the FOTW wouldn't KNOW what "Kryptonite" was in order to use it on Clark later. I remember thinking it stood out in the dialog because Clark would
normally say Kryptonite to Chloe post Arrival.
Swan told Clark in Rosetta what planet Clark was from: Krypton. Clark coined the term himself for the planet's meteorites. Kinda makes sense, actually, since all he did was add "ite" to Krypton. LOL