A cad is someone who behaves dishonourably or contemptibly dates from the early 19th century. It derives from the word cadet, which in the early 17th century meant a young lad or young servant before it acquired its later meaning of a young military trainee in the late 18th century. The word caddie is also another short form of cadet. Both cad and caddie came to describe young men who hung around looking for odd jobs or casual work. Perhaps those who did not get work resorted to unacceptable or caddish behaviour. By the mid-19th century, cad had become a term of contempt, while at the same time, caddie acquired respectable status as a golfer’s helper/attendant.