“The first profession to be labelled as ‘whistle blowers’ were the US police, who blew whistles to attract attention to wrongdoing. An early example comes from the newspaper The Janesville Gazette, June 1883, in a story about a policeman who woke half the town in order to forestall a riot: “Quiet was restored upon the arrival of the regular police force, and ere the town clock had struck the midnight hour all had returned to their homes. But the crowd of people were all willing to bet that McGinley was the champion whistle blower in America.”
It has also come to mean people who attempt to draw their superiors’ attention to something they believe to be wrong and, if they fail in that attempt and feel strongly enough about the matter, they go public.” from www.phrases.org.uk/meanings/whistle-blower.html
In my opinion whistle blowers are people who are trying to bring attention to a wrong in order to right it, and are brave individuals for doing so.