The story
From a quotation of Albert Einstein, "I, at any rate, am convinced that [God] does not throw dice" [Jedenfalls bin ich überzeugt, daß der nicht würfelt.], by which he expressed his dissatisfaction with the preeminence of probability in the Copenhagen interpretation of quantum mechanics. Einstein himself used variants of the phrase at different times. (See Albert Einstein on Wikiquote.Wikiquote ).
Etymology from Wiktionary, CC BY-SA 4.0.