The name of the mountain comes from the name of the Slavic god Perun. In the past, the mountain was bearing the name Orbelus given by the Thracians and means "snow-white". Its total area is 2,585 sq. km. Pirin has one of the most diverse flora and fauna from the Bulgarian mountains. The reason for this diversity is high altitude, south latitude and diverse relief. The presence of many lakes and streams creates perfect conditions for the rich flora. Pirin National Park is in the territory of the mountain. In Pirin flourish 18 local, 17 Bulgarian and 86 Balkan endemics. Local endemic species that grow here are unique and can not be seen anywhere else. The mountain is home to 31 species of birds and 5 species of mammals included in the Red Book of Bulgaria.