Sometimes, the more you stare at a word, the stranger it looks

"Jamais vu" (French for "never [before] seen") means that a known object or situation (or even a person!) seems strangely unfamiliar or odd. "Jamais vu" is sort of the opposite of deja vu ("already seen").

When the object that seems strange is a word, this is called "word alienation". Most people can induce word alienation by, for example, simply staring at the word "and" for several minutes. Another way is to write, for example, the word "door", very quickly 30 times per minute for a minute or two. Most people will experience the word seeming to become progressively odd, and the more you stare, the stranger it looks.

In the usual course of reading, a word has a form, a meaning, and a function in a sentence, and they are experienced briefly; when the word is instead viewed repeatedly, only the form of the word is experienced, and the form becomes progressively dissociated from the meaning.
It seems that being tired or having worked many hours often increases the probability of word alienation occurring.

http://www.abc.net.au/science/news/health/HealthRepublish_1689668.htm

http://en.wikipedia.org/wiki/Jamais_vu