Tetraphobia is an aversion or fear of the number 4 (four). It is a superstition most common in East Asia. The superstition is held because the Chinese word for four (四, pinyin: sì), sounds very similar to the word for death (死, pinyin: sǐ). The Sino-Japanese and Sino-Korean words for four, shi in Japanese and sa in Korean, sound identical to death in each language. I wonder if I am allowed to say: “I am going to hit you until you are four.”
It is not as I have been searching for more of these, but I am sure they exist. This photo was one I found by chance.