Hi S.,
I agree with the others....children are imitators...they repeat what they see and hear...it's how they learn.
My son is 7 1/2 yrs old and has yet to ever repeat a bad word. He knows that even stupid and idiot are not allowed because they are degrading to others. If he hears something at school he'll ask me what it means and we discuss it...whether it's an ok word or bad word.
So you really need to see who is around your son and who is influencing him. If it's other older children around him, they need to be told as well that certain words are not allowed in your house, and are not to ever be used at all. You said you work full time...does that mean he's at day care all day? Then I'd be questioning those in charge of the day care what they are allowing to go on where language is concerned. The kids should be learning respect for one another as they learn to interact and play..... they shouldn't be allowed to be saying inappropriate words...especially at their young age!
As far as breaking the habit...only you can know what works for your 2 yr. old son to get him to stop. If he has certain toys or something else that he likes....that can be threatened to be taken away if he doesn't stop using his potty mouth? Maybe time outs every time a bad one comes out of his mouth?
If he is very verbal and has great comprehension then maybe you can sit down with him and tell him why these words are bad....and that consequences will take place if he doesn't stop.
The flip side of all of this....is he doing it specifically for attention??? Has he caught on, knowing full well that when he's potty mouthing that he gets attention - good or bad - it's still attention.
If he's been told why it's bad, and does it anyway because of the attention, then some form of punishment will have to take place for him to get that it's the WRONG way to go about trying to get that attention.
But removing the 'source' of him learning all of the potty mouth words to begin with - is the first place to start.
Good luck....he's still young but hopefully compliant.
God Blessen