advogado do Diabo

The phrase traces back to the Catholic canonization process. From the late 16th century a Vatican official called the Promotor Fidei (Promoter of the Faith), popularly nicknamed the advocatus diaboli, was tasked with arguing against a candidate's sainthood so their case could be properly stress-tested. The role was formally established under Sixtus V in 1587 and only reformed in 1983 by John Paul II.