ParanoidObsessive posted...
That usually happens when someone says a word too many times in quick succession.
The phenomenon is called "semantic priming," and it mostly boils down to the fact that after hearing it so many times, your brain stops having to think about what the word means and is free to wander and start looking for other meaning/patterns in it (which often is hard to find because there aren't any, which is where the sense of weirdness comes from). A similar thing happens if you play a random voice clip repeatedly in quick succession, in that it starts to sound musical because your brain wanders and finds rhythmic/tonal patterns to focus on instead of having to think about the words.
Happening spontaneously, though, is just a brain fart.