M&M’s were created by Forrest Mars, the founder of the Mars company, and his business partner, William Murrie, the president of the Hershey company. Because both their last names started with “M,” they called their new candy M&M’s.
The idea came from seeing soldiers in the Spanish Civil War during the 1930’s eating chocolate pellets with a hard shell of tempered chocolate surrounding the inside, thereby preventing leaking. Production began in 1941. Murrie had a 20% stake in the product, Hershey’s having control of the rationed chocolate during WW2. They were an immediate hit with the military and have grown from there.