Why the 3Rd Degree?

The third degree is an intense, harsh way to question a suspect. ... It's very common for people to joke about the third degree, using it to mean "lots of questions" or "too much curiosity." The actual third degree is a cruel interrogation technique—essentially torture.

Why are you giving me the third degree?

To give someone the third degree means to interrogate them ruthlessly, to grill them without mercy, perhaps with threats or bodily harm. The idiom give someone the third degree came into use around the turn of the twentieth century in the United States to describe interrogations by some police departments.

What does it mean when you get the third degree?

informal. : a long and intense period of questioning The police gave him the third degree [=questioned him intensely].