The name flamingo comes from Portuguese or Spanish flamengo ("flame-colored"), which in turn comes from Provenal flamenc  a combination of flama ("flame") and a Germanic-like suffix -ing. The word may also have been influenced by the Spanish ethnonym flamenco ("Fleming" or "Flemish").
It is the Portuguese word for Flemish, and it was given to the nearby beach (Praia do Flamengo, Beach of the Flemish) because it was the place where the Dutch sailor Olivier van Noort tried to invade the city in 1599.