bug [L16th] For such a little word bug has a remarkably confused and complex history. Its origin is uncertain and use differs between British and American English. While Americans use bug for animals that the British would call *insects, the British use the term only for the bed bug or a certain order of insects called the Hemiptera, which include creatures such as the shield bug. From the late 18th century the British could use bug to mean someone who is a pest or nuisance or for a younger pupil at school, particularly a new bug. Other developments are originally American, although they spread to other Englishes. In the middle of the 19th century bug started being used for someone with an obsessive or enthusiastic interest. Later that century it became used for a fault in a machine, and then in the middle of the 20th century for a computer malfunction. Bug was also used for a germ from the late 19th century, and from the 1930s in yet another sense for a concealed microphone. As a verb meaning to annoy or irritate it is mid 20th century and originally jazz slang.