[Tervuren]

I think they like, use it whenever their mouth is like, running faster than their mouth is, so they feel the need to like, fill in a word to make up for like, the fact their brain isn't keeping up with like, their mouth.

There are two solutions - help them get smarter and faster in processing what they want to say, and increase their ready vocabulary, or get them to slow down how fast they talk. In simpler terms, slow the mouth down to a speed the brain can stay ahead, or speed the brain up to keep pace with the mouth. The former is probably the better option, but the best option is both. Thinking before, or even if, you say something, can make someone seem a lot wiser.