Arby's name comes from founders Leroy and Forrest Raffel.
The Raffel brothers founded the chain in Boardman, Ohio, in 1964. The name “Arby's” is a phonetic rendering of the initials R.B., referring to the Raffel Brothers. It is not an abbreviation for roast beef, although the chain became strongly associated with roast-beef sandwiches.
The brothers had experience in restaurant equipment and chose roast beef as the focus of their new business. Their menu and branding helped distinguish Arby's from hamburger-centered competitors.
Because “R.B.” sounds like “roast beef,” many people assume the name directly describes the signature sandwich. The explanation involving the Raffel brothers is the historical origin. Arby's later became a major franchised restaurant chain, but its name preserves the initials of the two founders rather than naming a food item.