Agitprop is a portmanteau of agitation and propaganda. The term originated in Bolshevist Russia (the future Soviet Union), i.e., Department for Agitation and Propaganda, which was part of the Central and regional committees of the Communist Party of the Soviet Union. The department was later renamed Ideological Department.
The term propaganda in the Russian language did not bear any negative connotation at the time. It simply meant "dissemination of ideas". In the case of agitprop, the ideas to be disseminated were those of communism, including explanations of the policy of the Communist Party and the Soviet state. In other contexts, propaganda could mean dissemination of any kind of beneficial knowledge, e.g., of new methods in agriculture. Agitation meant urging people to do what Soviet leaders expected them to do; again, at various levels. In other words, propaganda was supposed to act on the mind, while agitation acted on emotions, although both usually went together, thus giving rise to the cliché "propaganda and agitation".
The term agitprop gave rise to agitprop theatre, a highly-politicized leftist theatre originated in Europe of 1920s-1930s and spread to America as well, with plays of Bertolt Brecht being a notable example. Gradually the term agitprop came to describe any kind of leftist politicized art.
In the Western world, agitprop has a negative connotation. In the United Kingdom during the 1980s, for example, socialist elements of the political scene were often accused of using agitprop to convey an extreme left-wing message via television programmes or theatre.
After the Bolshevik Revolution, an agitprop train toured the country, with artists and actors performing simple plays and broadcasting propaganda. It had a printing press onboard the train to allow posters to be reproduced and thrown out of the windows if it passed through villages.