@Mammmood - That’s a good question. I don’t have the exact answer but I do believe I have what’s a viable theory. It was probably the process that they used for creating it that hinted at its potential for medicinal uses.
Remember that it was common to use fermented grapes. What do fermented grapes produce? They produce wine, and the ancients knew that wine was most certainly good for what ailed you.
So they probably reasoned from this that anything which reacted with these fermented grape leaves would be good for you as well. That’s my theory anyway.