Semantic Satiation
From Wikicliki
Semantic Satiation is when repeating a word or phrase causes it to temporarily lose meaning for the listener, who then processes the speech as repeated meaningless sounds.
When the phenomenon of semantic satiation was first reported in the literature around the turn of the century by investigators working in Titchener's Laboratory (Severance & Washburn, 1907), it was described as a curious and isolated effect and referred to as "lapse of meaning."