There was a young lady named Sue

Had to catch an express at two two

 Said the porter: "Don't worry

 Or hurry or scurry,

There's a minute or two to two two."

There was a young fellow named Tait

Had a date with his mate at eight eight

But I'd hate to relate

What that fellow named Tait

And his tete a tete ate at eight eight!

That sounds all right to me.

What did you have in mind?

I think its probably because as you repeat a word over and over you become less concerned about the meaning or context of the word and more aware of the fact that the word is just a random series of noises that your making! In context this does not sound unusual, everybody does it, however its is just filtered noise! 

Things you hear go in short-term memory, partly so you can replay them in your mind and detect further meaning in them. When they get transferred into long-term memory, what seems to go there is the semantic content - a more verbal, analysed version than the original oral one.

Repeating a word many times will probably fill up short-term memory, which would be a little disorienting, as any other sound and ideas you have would be displaced. In computer terms, you are flushing the cache.

Many methods of mind control use repetition of mantras, prayers, team chants, music, or self-hypnosis ("I will succeed! I will succeed!") to affect the continuity of the conscious mind, and thus engineer a state of mind that is open to change and/or closed from distractions.