A henchman or thug was a follower or supporter of a person, mostly a person behind a more powerful individual.
The Malurian agent Garos employed two henchmen while undercover mining on the Akaali homeworld. (ENT: "Civilization")
A criminal on Rigel X was accompanied by three henchmen who boarded Enterprise NX-01. (ENT: "These Are the Voyages...")
When James T. Kirk was stranded aboard the ISS Enterprise in the mirror universe in 2267, he noted in his captain's log that he witnessed how officers employ private henchmen among the crew and assassinate superior officers. (TOS: "Mirror, Mirror")
Sutok was followed by two henchmen when he came aboard Bahrat's space station in 2373. (VOY: "Fair Trade")
In the Dixon Hill series holoprogram, Nicky the Nose had a henchman who also tried to protect him from Jean-Luc Picard. (Star Trek: First Contact)
It was stated by Admiral Dougherty that petroleum turned thugs into world leaders on Earth and warp drive allowed Romulan thugs to create the Romulan Star Empire. (Star Trek: Insurrection)