Where does the phrase “Back Bay” come from and What does Back Bay mean?

Back Bay is a fashionable residential district of Boston, Massachusetts.

Formerly this was a basin of the Charles River, an inner harbor of Boston.

From 1856 it was gradually drained and filled in and laid out in fine wide streets, including Commonwealth Avenue, one of the finest boulevards in America.

Hence, used attributively, representative of the culture, thought, accent, etc., of Boston.