Although the origins of Craps are somewhat unclear and shrouded in mystery, there is no doubt that it has been around for a long time. There are differing opinions as to where Craps originated, it is almost certainly a descendant of Hazard. It is, however, also debatable where the game Hazard originated from. Claims have been made that Sir William Tyre, an Englishman, and his knights were the ones who invented the game during the time of the crusades. Those who believe that Sir William Tyre and his knights invented the game say that they used to play it to keep themselves busy while they were laying siege to a castle in 1125 AD. The castle's name was either Hazarth or Asart, and it is suspected that the similar sounding name stuck.
The Encyclopedia Britannica explains the name Hazard differently. The encyclopedia claims that Hazard comes from the words 'al zar' or 'azzah,' which means 'the dice.' The implication here would be that the game has at least some Arabic influence, and is likely to to be Arabic in origin.
Whether Hazard was invented by Englishmen or by others, it certainly became a very popular game for the English. It is mentioned often in the Canterbury Tales by Geoffrey Chaucer and the game has been played by the English over a number of centuries. The casinos of long ago, which were simply luxurious gambling houses, in the 17th century held Hazard games at which many noblemen and higher class Englishmen were able to lose many of their fortunes to the house. The formal rules of Hazard were shaped by Montmort.
The French Connection
There have been claims by the French that they were the ones who change the name of Hazard to Craps. This is unsubstantiated and most believe that the name "Craps" was coined in America. If a player throws a losing number 2 in Hazard, it is referred to as 'crabs.' The French claimed that they changed the name by changing slightly the losing 2's 'crabs' to 'craps.' Others believe that the French adopted the British name of Craps, but spelled it 'crabes' which seemed more French.
The History of Dice Games
Craps, being the ultimate dice game, is likely to have a link to the origins of dice games, which is nearly as far back as civilization itself. Cubical dice that are around 2600 years old have been found in Egypt. As explained above, there may also be the Arabic connection. The ancient Roman connection, however, seems to have a more direct link with the Craps we know today.
The Roman Empire
There are those who believe that Craps began with the Roman Empire. Both Caesar and Caligula were known to be dice players, as were many of their contemporaries. Roman soldiers used to play a game with shaved down pig knuckles, which were shaped into cubes (dice). They used to throw these cubes into their upside down shields.
As to answering the question, "Where did it really come from?," there seems to be no clear answer, however, there is much food for thought!