pirarucú
/pɪˈˌrɑːrəˌˈkuː/(also pirarucu, piraracú)
noun
The arapaima, a very large food fish of the Amazon basin, Arapaima gigas (family Osteoglossidae) that is one of the largest freshwater fishes in the world.
Origin
Mid 19th century; earliest use found in Robert Schomburgk (1804–1865), surveyor and traveller. From Portuguese pirarucu from Tupi pirauru'ku from pi'ra fish + uru'ku red tincture, red paint, so called on account of the red colour of the border of its scales.