who introduced probability?

Answer 1

As for classical probability, it was probably Abraham de Moivre and Blaise Pascal.
As for modern probability in its current sense, it was A.N. Kolmogorov in the 1930's.

Answer 2

I can't remember if it was Cain or Abel. On second thought, it was probably Eve.

Edit:
My point was that the origin of probability is lost in antiquity. The word probable comes from the Latin probabilis, and the word, probability, evidently appeared in Middle English circa 15th Century.

Ancient gamesmen certainly calculated probabilities , or odds, to give themselves an edge over their victims, while maintaining an appearance of fairness. They didn't publish, as that would have destroyed their advantage, thus making their games less desirable.

Pascal, according to the history taught when I was in school, was disgusted at being ruped at one or more of these games of chance, and set out to publish the probabilities involved, and derived the means of calculating most probabilities. Wikipedia gives a slightly different account of his involvement in the field. He justly deserves credit for the first definitive work published on the subject.

Answer 3

Blaise Pascal perhaps, on his study about games of chance