A<unk>  (from Latin meaning 'hair nest') is a blanket term for any type of skin infection near the tailbone.  
It is a combination of two Latin words, pilus, meaning hair and nidal, meaning nest. The condition is now referred to as<unk>  sinus disease.
The term<unk> " can be misleading, as a majority of the time, this is actually an abscess.
Pilonidal cyst
Pineal gland cyst
Scrotal cyst
Hidrocystoma
Spermatocele
Epididymal head cyst
Testicular cyst
Nabothian cyst