Because the concept of the secular is normally conceived as standing in opposition to religion many people may not realize that it originally developed within a religious context. This may also come as quite a surprise to religious fundamentalists who decry the growth of secularism in the modern world.
Read Article: Religious Origins of Secularism

Thank you for this concise history of secularism. Lots of good info. here for the student (me).
The quoted paragraph is especially interesting to me, and it bears further investigation. Theologians saying that revelation “necessarily” causes contradictions is an amazing idea!