What causes people to adopt an overused word?

Usually, it’s a simple word or phrase such as “like” or “you know what I mean?” but it can be far more strange.

Back when my wife and I were newlyweds, we had an apartment in a complex in Santa Barbara. The building superintendent/maintenance guy had a heavy Italian accent, and somehow had adopted the word “eventually” as a pet word. You never knew when it was coming, but eventually, whether he was talking about a leaky faucet or a scheduled inspection, the word “eventually” would eventually get into every single sentence that came out of his mouth. It often didn’t even make any syntactic sense, it just eventually got tossed randomly into the sentence. Perhaps it helped him eventually stop one thought and move to the next. We eventually started calling him “eventually” when talking between ourselves.

My wife just mentioned him, and it made me wonder what strange thought process causes us to adopt an overused word or phrase, and why are we personally so oblivious to it? What do you think causes it? What does someone’s having an overused word tell us about its user’s thought process? Does the choice of word tell us anything, or is it adopted randomly, through some sort of imprinting process at the time the need for a “crutch” word or phrase arises?