Douglas Harper's Etymology Dictionary
1922, member of Fasci di Combattimento, Italian paramilitary unit founded 1919 by Mussolini; so called for their uniforms.
Wikipedia
Black Shirt (Italian: Camicia nera) is a 1933 Italian drama film directed by Giovacchino Forzano. The film was made by the Istituto Luce as a propaganda work to commemorate the tenth anniversary of Mussolini's Fascist regime. It portrays events in Italy from the beginning of the First World War to the coming to power of Mussolini and the transformation of the country since. It combines elements of normal fiction films, documentary and futurist influences.
The film The Old Guard, released the following year, is also set in the period leading up to the March on Rome.
Usage examples of "black shirt".
Father Piotr was casually dressed in jeans, black shirt, white Roman collar of his profession, and a light, buttoned sweater.