From the founding Warner brothers, the company name originated. The 3 elder brothers begin in the film theater business. They acquired a film projector and in the mining towns of Ohio and Pennsylvania, they showed films. In 1903 Sam and Albert opened their first theater the Cascade in New Castle, Pennsylvania. The Pittsburgh-based Duquesne Amusement & Supply Company in 1904 to distribute films was founded by Warners.
Warner Brothers began producing films by the time of Worl War One. The 1st studio was opened on Sunset Boulevard in Hollywood in 1918. Sam and Jack produced pictures and Harry and Albert handled finance and distribution. During World War One their 1st film My Four Years in Germany released. On April 4, 1923, they formally incorporated as Warner Bros. Pictures, Incorporated.
Source: https://pdqwire.com/warner-brothers-the-journey-to-become-big-5-major-american-film-studios/