"The term in its present form is 19th century. Anthony Trollope, in his work Australia and new Zealand, 1873 observed: 'In the colonies... when a gentleman sounds his own trumpet he 'blows.' That is clearly commenting on what must already have been a well-known phrase, although there aren't known printed citations to support that from before 1873." Read more about it here . When people use the phrase they are saying the person is being boastful and self-promoting.