Audi traces its history back to 1899 when August Horch established a brand, Horch, to compete with Benz and Mercedes. Horch had a dispute with his business partners and he left the company. Since he no longer owned the rights to his own name, he started a new company, naming it “Audi,” Latin for horch or “hark.” In 1932, Audi joined forces with three other companies to form Auto Union. The original four companies of Auto Union are represented by the overlapping rings of the Audi logo.
Source: I Am Audi Forum