Origin of "Third Degree"

If we are given the "third degree", we are interrogated fiercely. The association with interrogation is believed to come from masonic practice. In the 19th century, when the masons were still regarded as a powerful, illicit group, there were many rumours about their secret rituals. Part of the initiation to become a third degree master mason (one of the highest ranks in freemasonry), was rumoured to involve a long, intense interrogation, and by the start of the last century, the phrase "to be given the third degree" was already being used to describe a particularly brutal police interrogation.