where did it get the name from?
Giant otter" translates literally as "nutria gigante" .and "lontra gigante" in Spanish and Portuguese
Giant otter
"Giant otter" translates literally as "nutria gigante" and "lontra gigante" in Spanish and Portuguese, 
what is giant otter? It is a South American carnivorous mammal.
wiki:18404857
Giant otter [SEP] Naming
The giant otter has a handful of other names. In Brazil it is known as "ariranha", from the Tupí word "ari'raña", meaning water jaguar (). In Spanish, river wolf () and water dog () are used occasionally (though the latter also refers to several different animals) and may have been more common in the reports of explorers in the 19th and early 20th centuries. All three names are in use in South America, with a number of regional variations. "Giant otter" translates literally as "nutria gigante" and "lontra gigante" in Spanish and Portuguese, respectively. Among the Achuar people, they are known as "wankanim", and among the Sanumá as "hadami".