The term documentary has evolved over the years as a 'film-making practise' and a 'cinematic tradition' which enhances audience feedback, before, during or after filming.
The word DOCUMENTARY was first originated in 1926 in a review of Robert Flaherty's Moana, published in the New York Times. 
Pre 1900:
The beginnings of film development began prior 1900. People were beginning to test shots and single shot movements were being created and captured such as a train entering a station or a boat docking.
Very little story-telling commenced before the twentieth century due to technological difficulties, so in a way making it difficult to have audiences respond in feedback as little comment could be made.
Throughout the beginnings of the 1900's, documentary films were almost being made subconsciously, without being labelled.
- The french surgeon Eugene Louis Doyen started a series of surgical films, saying that even his own films helped him to correct professional mistakes/errors.
- Between 1898 and 1901, the Romanian professor Gheorghe Marinescu made several science films. The professor called his work 'studies with the help of cinematograph'
Romantisism:
With the help of Robert J. Flaherty's Nanook Of The North in 1922, documentary film embraced Romanticism. The documentaries usually showed how his people lived 100 years earlier and not how they lived right now.
This draws a link to the films made by Marinescu and Doyen as they are created in order to educate or inform audiences.
Here is a short clip of the documentary Nanook of the North (1921):
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Russia's developments in documentary film flourished in the 1920's with the seizure of power by the Bolsheviks party (1917) when heavy propaganda and controlling regimes were implemented.
Dziga Vertov was a Soviet Pioneer Documentary Film-Maker who worked central to the Soviet-Kino Pravda ("cinematic truth").
- He believed that the camera could render more of a reality than the human eye, yet his work completely juxtaposed this philosophy due to the propaganda used to brainwash the public.
A similar influence would have been Joseph Goebbels who worked as the Reich Minister of Propaganda under the ruling of the Nazi's throughout Germany.
He used his documentary propaganda, along with other sources to psychologically prepare the German people for aggressive war as well as accusing many German ethnics and national minorities (such as homosexuals, The Jews, The French and The Pols) of trying to destroy Germany, claiming any unjust actions as self-defence.
Here is an example of Goebbels's work:
Here is a clip from the film 'The Boy In The Striped Pyjamas', there is a good example of a remade example of a Nazi Propaganda film, promoting concentration camps in a documentary style.
(Skip to 1 minute)
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Cinema Verite: (1950's-1970's)
Such technology advances meant there were not as many constraints against studio based film production. This meant that smaller crews could film on location where film-makers could take advances in technology allowing smaller, hand-held cameras.
This could almost be seen as the time when documentaries were split into sub-genres concerning degrees of involvement with the subject.
There are important differences between Cinema Verite and the North American 'Direct Cinema' concerning the ways in which it is shot with the use of interviews, observational styles, hand-held movement, on screen presentation etc.
