You might not believe it but there are people who are actually afraid of moon and when we say afraid, it is not just a slight discomfort, it is a full blown phobia and is known as selenophobia. Even though you might not encounter people who suffer from this phobia even once in your life, it is very real and it does plague the lives of some people and make it hard for them to operate normally in their daily life. Generally phobias are so deep rooted that it is hard for the patient to overcome them without any professional help but they do not always get this help which is why they suffer.
Due to unawareness, people always mock patients who suffer from phobias and often trivialize the phobias which has negative effect on the patient and often gives birth to anxiety, depression and many other things. If you find this particular phobia interesting, wish to get knowledge about it or know someone suffering from it and want to help them then you can go to https://massivephobia.com/selenophobia-fear-of-moon/.
It is not a common phobia so there is not a lot of research on it but when we talk about causes, there does not seem to be a specific one, it is more likely a phobia that is caused by superstition either of the person or transferred by parents. Often people develop this fear that night time is dangerous and when that fear worsens, it can often transform into selenophobia. If it is a fear that is transferred by the parents then the patient would be suffering from it since childhood and it can well go on in adulthood and would not go away till it is treated through proper channels and therapy sessions.