It's the usual practice that some things appeared in our life too many years ago for their roots to be remembered. Probably that's why the case of the sandwich invention is not as well-known as it should be while its history goes deep into the 18th century.

The famous snack took its name after John Montagu, who is also known as the 4th Earl of Sandwich.

The story tells us that the dish was contrived by Montagu purely by chance. He appeared to be a passionate gambler and during one of the hot card games he found no time for breakfast or lunch. After several hours of unstoppable gambling, the Earl got hungry but the desire to go on with the fun was even stronger than his hunger. So the Earl decided to find a compromise. He ordered the servants to roast a thin beefsteak. Then the beefsteak was wrapped in cheese and put right between two bread slices.

Thus, by inventing this snack he managed to satisfy his hunger and went on playing without interruptions.

More Info: en.wikipedia.org