An anaconda is a large, non-venomous snake

Snake

Snakes are elongate, legless, carnivorous reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears. Like all squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales...

 found in tropical South America

South America

South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...

. Although the name actually applies to a group of snakes, it is often used to refer only to one species in particular, the common or green anaconda, Eunectes murinus, which is one of the largest snakes in the world.

Anaconda may refer to:

• Any member of the genus Eunectes
  Eunectes
  Eunectes is a genus of boas found in tropical South America. They are an aquatic group of snakes and include one of the largest snakes in the world, E. murinus, the green anaconda. The name Eunectes is derived from the Greek word Eυνήκτης, which means "good swimmer"...
  
  , a group of large, aquatic snakes found in South America.
• Eunectes murinus, a.k.a. the common anaconda, the largest species, found east of the Andes in Colombia, Venezuela, the Guianas, Ecuador, Peru, Bolivia, Brazil and on the island of Trinidad.
• Eunectes notaeus
  Eunectes notaeus
  Eunectes notaeus is a non-venomous boa species found in South America. No subspecies are currently recognized.-Description:Adults are not as large as the green anaconda, E. murinus, but nevertheless grow to an average of in length. The maximum size is almost certainly larger...
  
  , a.k.a. the yellow anaconda, a smaller species found in eastern Bolivia, southern Brazil, Paraguay and northeastern Argentina.
• Eunectes deschauenseei
  Eunectes deschauenseei
  Eunectes deschauenseei is a non-venomous boa species found in northeastern South America. No subspecies are currently recognized.-Geographic range:...
  
  , a.k.a. the dark-spotted anaconda, a rare species found in northeastern Brazil and coastal French Guiana.
• E. beniensis, a.k.a. the Bolivian anaconda, the most recently defined species found in the Departments of Beni and Pando in Bolivia
  Bolivia
  Bolivia officially known as Plurinational State of Bolivia , is a landlocked country in central South America. It is the poorest country in South America...
  
  .
• The giant anaconda
  Giant anaconda
  Reports of giant anacondas date back as far as the discovery of South America when sightings of anacondas upwards of 50 meters began to circulate amongst colonists and the topic has been a subject of debate ever since among cryptozoologists and zoologists.Anacondas can grow to sizes of and...
  
  , a mythical snake of enormous proportions found in South America.
• Any large snake that "crushes" its prey (see Constriction
  Constriction
  Constriction is a method used by various snake species to kill their prey. Although some species of venomous and mildly-venomous snakes do use constriction to subdue their prey, most snakes which use constriction lack venom. The snake initially strikes at its prey and holds on, pulling the prey...
  
  ). Applied loosely.

Etymology

As per National Geographic, the word anaconda comes from the Tamil

Tamil language

Tamil is a Dravidian language spoken predominantly by Tamil people of the Indian subcontinent. It has official status in the Indian state of Tamil Nadu and in the Indian union territory of Pondicherry. Tamil is also an official language of Sri Lanka and Singapore...

 word anaikolra, which means elephant killer.

The name was first used in the English language in 1768 by R. Edwin in a colorful description of a large snake found in Ceylon (now Sri Lanka

Sri Lanka

Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka is a country off the southern coast of the Indian subcontinent. Known until 1972 as Ceylon , Sri Lanka is an island surrounded by the Indian Ocean, the Gulf of Mannar and the Palk Strait, and lies in the vicinity of India and the...

), most likely a reticulated python, Python reticulatus. The account, which explains how the snake crushes and devours tigers, is full of popular misconceptions, but was much read at the time and so gave rise to the myth of the Anaconda of Ceylon.

Various theories exist regarding the origin of the name itself. One suggests that it was derived from the Sinhala henakandaya. However, this name is used to refer to the brown vine snake, Ahaetulla pulverulenta

Ahaetulla pulverulenta

Brown-speckled Whipsnake Ahaetulla pulverulenta is a species of tree snake found in the Western Ghats of India.-Description:Snout pointed, terminating in a dermal appendage which is longer than the eye, formed below by the rostral, and covered above with numerous small scales or warts; the length...

, a slender arboreal species that grows to five feet (152 cm) at most and feeds only on small vertebrates. Another theory by Yule and Burnell (1886) is based on an entry in the Catalogue of Indian Serpents from the Leyden Museum (Ray, 1693) that reads: Anacondaia Zeylonensibus, id est Bubalorum aliorumque jumentorum membra conterens, meaning "the anacondaia of the Ceylonese, i.e. he that crushes the limbs of buffaloes and yoke beasts." Without a clear Sinhala connection, they suggest one from the Tamil language

Tamil language

Tamil is a Dravidian language spoken predominantly by Tamil people of the Indian subcontinent. It has official status in the Indian state of Tamil Nadu and in the Indian union territory of Pondicherry. Tamil is also an official language of Sri Lanka and Singapore...

instead: anai-kondra (anaik-konda), meaning "which killed an elephant.”