According to the Post Cereal website, the name is believed to come from the "grape sugar" that formed while baking, and the "nutty" flavor that they had. See related link.
I have grown up in a grape growing region and have never seen a flower on a grape vine. The "baby" grapes are small nubs on the vine, but don't flower. If you have a vine with a flower it isn't grape.
If you have grape vines, but no grapes, then there is something wrong with the vines or you're looking for grapes at the wrong time of year and they just haven't come yet. I'd suggest moving the...