pira sainha

Piranha comes from Tupi pira (fish) + sainha (tooth) or añá (scissors). It's 'toothed fish' or 'scissors fish' — named for what makes it fearsome.

Portuguese colonizers encountered piranhas in Brazil and borrowed the Tupi name. The fish's reputation for stripping carcasses to bone spread with the word.

Theodore Roosevelt's 1913 expedition popularized piranha terror in America. His guides staged a piranha 'feeding frenzy' that became legendary.

Now 'piranha' is metaphor for anything that devours rapidly: piranha investors, piranha journalists. The fish became a symbol.