'Paradise' as in the Garden of Eden, where the biblical Book of Genesis depicts the first man and woman living in, and falling from, a state of divine innocence. Here Freud boldly states that the Judao-Christian creation scripture is no more than a 'mass fantasy', recalling only the personal fall from innocence each person experiences as they leave childhood. His perception of organised religion as a form of comforting but ultimately crippling mass-neurosis would be more comprehensively explored in later works.
Online edition of the King James Version 'Book of Genesis', at BibleGateway.com
Online edition of Freud's 'Civilisation and its Discontents', translated by James Strachey, (originally published 1930)