The word Henchman referred originally to one who attended on a horse, that is, a groom. Hence, like groom, henchman was the title of a subordinate official in a royal or noble household.
The first part of the word comes from the Old English hengest, meaning "horse". The word also occurs in many Teutonic languages, such as German and Dutch as hengst. The word appears in the name Hengest, the Saxon chieftain, and still survives in English in placenames and other names beginning with Hingst- or Hinx-. It was often rendered as Henxman in medieval English.
Henchmen, pages of honour or squires, rode or walked at the side of their master in processions and the like, and appear in the English royal household from the 14th century until Elizabeth I abolished the royal henchmen, known also as the children of honour.
The word became obsolete in English from the middle of the 17th century, and seems to have been revived through Sir Walter Scott, who took the word and its derivation, according to the New English Dictionary, from Edward Burt's Letters from a Gentleman in the North of Scotland, together with its erroneous derivation from haunch. The word is, in this sense, synonymous with gillie, the faithful personal follower of a Highland chieftain, the man who stands at his masters haunch, ready for any emergency. It is this sense that usually survives in modern usage of the word, where it is often used to describe an out-and-out adherent or partisan, ready to do anything.
Henchmen are common in mystery, fantasy, adventure comic books, and adventure novels and movies. They are the expendable adherents of the head villain, always ready to do his bidding, to kill or be killed, kidnap, or threaten, as needed. They are either killed by the hero before he can get to the main villain, killed by the hero's sidekick in a dramatic battle, or even get killed by the main villain himself as punishment for failure to comply to orders. Henchmen in this sense are also sometimes called lackeys.
A henchman might also be the NPC (non-player character; computer controlled) follower of a PC (player character) in computer RPGs (role-playing games). This henchman will follow the player around and assist him/her in various manners. In fiction, such supporting characters are normally tied to the hero by bonds of friendship and loyalty, because of which they are usually called sidekicks; the villain's supporters are called henchmen because his villainous nature makes such bonds difficult to establish. Every villain in many Television programs, such as Batman (TV series) had henchmen, usually dressed in costumes reminiscent of the villain's.