The term Cubism did not come into general usage until 1911, mainly with reference to Metzinger, Gleizes, Delaunay, and Léger. In 1911, the poet and critic Guillaume Apollinaire accepted the term on behalf of a group of artists invited to exhibit at the Brussels Indépendants. The following year, in preparation for the Salon de la Section d'Or, Metzinger and Gleizes wrote and published Du "Cubisme" in an effort to dispel the confusion raging around the word, and as a major defence of Cubism (which had caused a public scandal following the 1911 Salon des Indépendants and the 1912 Salon d'Automne in Paris). Clarifying their aims as artists, this work was the first theoretical treatise on Cubism and it still remains the clearest and most intelligible. The result, not solely a collaboration between its two authors, reflected discussions by the circle of artists who met in Puteaux and Courbevoie. It mirrored the attitudes of the "artists of Passy", which included Picabia and the Duchamp brothers, to whom sections of it were read prior to publication. The concept developed in Du "Cubisme" of observing a subject from different points in space and time simultaneously, i.e., the act of moving around an object to seize it from several successive angles fused into a single image (multiple viewpoints, mobile perspective, simultaneity or multiplicity), is a generally recognized device used by the Cubists.

What year did the term Cubism become used more?