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.
Fla Flu (a truncation of Flamengo Fluminense) is an association football match between cross-town rivals Flamengo and Fluminense. Matches take place in the 78,000-seat Maracan Stadium, located near downtown Rio de Janeiro, in the city's Maracan district.