Middle English, from Old English hengest 'male horse' + man, the original sense being probably 'groom'. In the mid 19th century the sense 'principal attendant of a Highland chief' was popularized by Sir Walter Scott, whence the current (originally US) usage.

• The original sense of this was probably ‘a groom’. It is from Old English hengest ‘stallion’, and man. The first part also features in the names of the semi-mythological leaders Hengist and Horsa (meaning ‘horse’), who supposedly came to Britain at the invitation of the British King Vortigern in 449 to assist in defeating the Picts. From the Middle Ages a henchman was a squire or page of honour to a person of great rank; in Scotland he was the principal attendant of a Highland chief. The word was taken up by Sir Walter Scott, whose novels were hugely popular throughout the 19th century, and Scott gave henchman to the wider world. The current sense, ‘a criminal's follower’, began in the mid 19th century in the USA.