In gambling

Gambling

Gambling is the wagering of money or something of material value on an event with an uncertain outcome with the primary intent of winning additional money and/or material goods...

, snake eyes is the outcome of rolling the dice

Dice

A die is a small throwable object with multiple resting positions, used for generating random numbers...

 in a game and getting only one pip on each die. The pair of pips resembles a pair of eyes, which is appended to the term 'snake' because of the long-standing association of this word with treachery and betrayal. The dictionary of etymology

Etymology

Etymology is the study of the history of words, their origins, and how their form and meaning have changed over time.For languages with a long written history, etymologists make use of texts in these languages and texts about the languages to gather knowledge about how words were used during...

 traces that use of the term back to 1929, although it may be traced all the way back to the ancient Roman

Ancient Rome

Ancient Rome was a thriving civilization that grew on the Italian Peninsula as early as the 8th century BC. Located along the Mediterranean Sea and centered on the city of Rome, it expanded to one of the largest empires in the ancient world....

 dice games, where 'Dogs' represented two ones. They referred to this as "the dog throw". In modern parlance, it refers to such a roll in any game involving dice. Snake eyes also refers to looking one way and passing the ball the other in the game of Taps.

Games

Because this is the lowest possible roll, and will often be a loser in many dice games, such as Craps

Craps

Craps is a dice game in which players place wagers on the outcome of the roll, or a series of rolls, of a pair of dice. Players may wager money against each other or a bank...

, the term has been employed in a more general usage as a reference to bad luck

Bad Luck

Bad Luck may refer to:* Harmful or negative luck* Bad Luck , a 1960 film directed by Andrzej Munk* "Bad Luck" * "Bad Luck" * Bad Luck, an album by Trophy Scars...

.
In many board games such as Monopoly

Monopoly (game)

Marvin Gardens, the leading yellow property on the board shown, is actually a misspelling of the original location name, Marven Gardens. The misspelling was said to be introduced by Charles Todd and passed on when his home-made Monopoly board was copied by Charles Darrow and thence to Parker...

, house rules

House rules

House rules are rules applying only in a certain location or organization. Bars and pubs in which games take place frequently have house rules posted...

may decide that rolling Snake Eyes (or any Doubles) leads to a bonus since they are rarely rolled.

Probability

Rolling two 6-sided dice gives you a chance of 1 in 36 chance of getting a snake eyes each time you roll the dice.

Rolling two 6-sided dice 25 times gives a probability of .505532 that at least once, snake eyes will appear.