It comes from the Latin “Securus Judicat Orbis Terrarum!”, which means “The verdict of the whole world is conclusive!”
It was said by St. Augustine about the Catholic Church and by this he meant that the Church had stood together as one, united for the truth. It implies that the truth is fact, supported by the Bible, rather than something we could argue about.
Are you sure the passage isn't something about the fathers of the church - who were firm in their belief that the Catholic Church was the source of all truth?