Quoting Frank Schäfer:
One the theories about the origin of the name oscars says it comes from an article on Astronotus that was published by E. W. Clarke in the journal The Aquarium in 1936.
Clarke owned a couple named Lena and Oscar.
In 1949, Gene Wolfsheimer reported in The Aquarium Journal that California aquarists named Astronotus cichlids as Oscars (Wayne Leibel, Aquarium USA Annual 2001).
But it is also conceivable that the word "Oscar" is a corruption of the scientific name (i.e. Astronotus) or the Tupi word for all possible larger cichlids "Acara". Tupi is the language of the people who originally lived in Brazil before the arrival of Europeans in America.