"Blackshirt" is a derrogatory term for Council Security. (TOS: "Greetings From Earth"). It is akin to the use of the word "pig" to describe a civilian officer of the law.
Notes
- In the real world, the term "Blackshirt" was used for paramilitaries supporting Mussolini's fascist regime. Cf. "Redcoat".
- The term may also have been inspired by the Nazis' Stormtroops (SA), which were called "brownshirts" because of their brown uniforms.