Any word in any fucking lexicon will start to sound funny if you repeat it aloud enough times. That's because after hearing a word x times, your mind starts to realize that there's no context associated with it, and therefore it lacks the meaning(s) it would have under normal circumstances. Your mind starts to analyze the sounds that make up the word, and the actions that are being taken by your vocal cords, tongue, teeth and nasal passages to create the sounds.

Talking is something that you probably do often enough that your spinal cord can takes care of it most of the time. When your conscious mind starts examining it, though, you start to realize how silly the whole process is. Words have symbolic meaning, as opposed to pictures, which inherently refer to the things they represent. If you take away the meanings of a word, then it becomes pointless to go through the act of saying it; the longer you continue to say the word, the more apparent this becomes.