A condition in the skin of the buttocks where small holes form along the crease. The holes lead to a subcutaneous pocket that usually contains loose hairs and inflamed tissue. The name 'pilonidal' comes from Latin and means 'nest of hair'.
Yes, these are common folk names for the same disease, although they are not medically anatomically accurate.
No. It is an acquired disease that develops during life, usually around the teenage years.
No. It is caused by inflammation of the hair follicles and fat in the skin in the buttocks, not by contagion.