Usage 1: The noun, "prodigy," refers to someone with a prodigious talent. In the 18th century, the adjective was use as an intensifier, like "really," "very," and so on: "It was a prodigiously fortuitous accident that allowed my wife and me to meet for the first time" is a sentence (not to say a mouthful) fitting for a romance. The word no longer serves that function.
Suggested usage: Today, you can speak of a child's prodigious talent for painting or your great-aunt's prodigious ability to upset everyone at family gatherings, or the prodigious amount of cat hair on the couch. It now refers to an enormous or extraordinary amount of something.
Etymology: Latin prodigiosus "monstrous or portentous" from prodigium "an omen, portent."