You’re trying to spell the word niehbor. Nieghbor. Neigbhor. Neighbor. Or you repeat a word aloud several times, “Gallop… gallop… gallop… gallop…” The word becomes meaningless sounds on your tongue. The subject has been a curiosity for a long time. Elizabeth Severance and Margaret Washburn wrote on the topic in 1907:
“If a printed word is looked at steadily for some little time, it will be found to take on a curiously strange and foreign aspect. This loss of familiarity in its appearance sometimes makes it look like a word in another language, sometimes proceeds further until the word is a mere collection of letters, and occasionally reaches the extreme where the letters themselves look like meaningless marks on the paper.” (Minor studies from the psychological laboratory of Vassar College: The loss of associative power in words after long fixation.).
This is now referred to as semantic satiation. There’s a name for everything isn’t there?
How it occurs is remains unconfirmed. The current leading hypothesis (by Leon Jakobovits James at McGill University, 1962) claims that the neural pathways activated in the brain are silenced as noise. A wonderful example of this happening can be seen in the “disappearing colors illusion”. Stare at the dot in the center of the below image and the colors will slowly fade away.
Staring at the dot in the image opens specific neural pathways in your vision center. Keeping those pathways active for too long with cause the brain to ignore those pathways as noise, fading the color to white. The same is purported to happen when repeating a word too many times.