It began at the Bauhaus, an art-and-design school founded in Weimar, Germany in 1919. Rejecting decoration for its own sake, it held that geometric primitives and primary colors alone could produce clear, functional form — famously formalized in Johannes Itten's color theory pairing circle with blue, triangle with yellow, square with red.
Typographically it favored sans-serif type (radical for its time) and asymmetric grids, with experiments in all-caps or all-lowercase setting. Many of today's geometric sans-serifs — Futura, Helvetica — descend from this lineage.
From architecture and furniture (the Wassily Chair) to brand logos and today's minimal sans-serif UIs, it's one of the taproots of modern design, and still the reference point whenever a composition needs an "organized geometry" mood built from a few shapes and primary colors.