From H Roy Elseth’s Did God Know?:
The English word “foreknowledge” generally means knowledge of something before it happens, exists, or comes into being. It usually connotates certain knowledge – i.e. the event must happen or occur otherwise the person did not have “foreknowledge.” The Greek word found in the forms “proginosko, prognosis, and proginosken” is decidedly different. It means to predict what will happen, exist or come into being.
Proginosko carries with it the idea of past knowledge, to know beforehand, or even foresight, whether human or divine. It is rooted in a medical term originating in the time of Hippocrates and means almost exactly what our English counterpart word, prognosis, means. In medicine, it is the prediction of the probable course of the disease and of the chances of recovery based on present knowledge. In other words, it is a prognosis based on diagnosis…
However, when interpreting them in context of Scripture a strong theological twist was added. It seemed as if the scholars were trying to force a meaning upon proginosko [foreknowledge] which it really doesn’t have. They get in real trouble when they find that both Luke and Peter apply this same word “proginosko” [foreknowledge] not only to God, but also to man.