Tetraphobia

Tetraphobia (from tetra, Greek for "four") is the fear of the number 4. It is mainly suffered in several Asian countries like China, Vietnam, Korea, and Japan, as well as those ethnic groups in other parts of the world. The reason for this fear is that the word four rhymes with death in their native languages. So people suffering from tetraphobia may readily lead to the development of thanatophobia (fear of death).