This is a comment to a closed discussion, but always relevant.
The most effective way to stop a two year old repeating something is simply to repeat it back to them. "Yes darling" is not enough. They need to hear confirmation that what they are saying is correct, as well as the fact that you've heard them correctly. There are times when they'll get a few things mixed up or the words aren't quite right, and if you repeat back to them correctly then they will soon learn and their language skills will continue to improve.
This discussion is related to 2 YO with repetitive speech pattern