Keno is a lotto game in which several numbers (typically 20) are drawn from a large field of numbers (typically 80). Players select a set of numbers from the main field (usually a minimum of 3 numbers up to a maximum of 10 numbers) and are awarded prizes based on how many of their numbers match those in the drawn set.

According to an ancient scroll, keno history started in China. Apparently ancient Chinese scrolls indicate that Cheung Leung of the Han Dynasty introduced a game similar to keno around 200 BC. Cheung's city was at war for several years and was beginning to run out of supplies. Rumor has it that the citizens of his city refused to contribute any more to the war fund, so Cheung created a game of chance to produce revenue for his army. This game, a numbers game not unlike keno, was an instant success and played a great part in saving the city. 

Quickly spreading throughout China, keno was also used to help fund the building of the Great Wall. The game also became known as the White Pigeon Game because carrier pigeons were used to send the winning numbers from the keno games in the larger cities to small villages and hamlets.

The heritage produced by this keno history is a Chinese poem of a thousand numbers. The 'thousand character classic' as it is known is a set of independent characters placed in a rhymed form. Originally a new way for children to learn, the poem is so well known the characters are often used as a romantic numbering system. So instead of having a board of just numbers on the original keno boards, they used these characters. Originally as many as 120 characters were used in the game, only after it left china would the number drop to a more familiar 80.

From there, the story gets a little dull. Basically the most common theory is that Chinese immigrants imported the game as they helped construct the railroad in the old west. Regardless of its illegality, keno was played continuously by Chinese immigrants, so much so that in and around cities like San Francisco it became known as the Chinese lottery. 

The game didn't have much success making its way into mainstream North American culture while it continued to use the Chinese characters as numbers. Keno history didn't evolve further until near the end of the 19th century when the characters were replaced with more familiar numbers.

In classic American style, when gambling was legalized in the state of Nevada in 1931 the fact that lotteries were not covered under the legislature discouraged no one. All they had to do was change the name of the 'Chinese lottery' to something else, so that it wasn't a lottery anymore. 

Thus, it was changed to 'horse race keno', playing off of the idea that the numbers are horses and you want your horses to come in. As the government passed a law that taxed off-track betting, so the name was changed once again to offer a better profit. And that's how the game got its name – Keno.