The OED lists five senses of the noun prodigy from Latin prodigium. The date range for the examples given for each of them are shown.
An extraordinary thing or occurrence regarded as an omen; a sign, a portent. Now rare. Circa 1450 - 1991
An unusual or extraordinary thing or occurrence; an anomaly; something abnormal or unnatural; spec. a monster, a freak. 1595 - 2004.
3a. An amazing or surprising thing; a wonder, a marvel. 1616 - 1988
3b. A wonderful or outstanding example of a specified attribute, achievement, etc. 1647 - 1993
3c. A person with exceptional qualities or abilities esp. a precociously talented child. Frequently with appositive modifying word, as child prodigy, infant prodigy, etc. 1684 - 1991
Hence, all of them have relatively current entries. However, sense 1 seems to reflect the meaning you describe of a prodigy being "demonic", and in that case there is no entry between 1882 and 1991, and the latter does seem to refer back to a classical matter. Those two examples are given below, and I would therefore deduce that the the omen,sign,portent meaning ceased around the end of the nineteenth century.
1882 F. W. Farrar Early Days Christianity I. 73 The air was full of prodigies. There were terrible storms; the plague wrought fearful ravages.
1991 Classical Q. New Ser. 41 318 The prodigy of Hippokrates' pots overboiling firelessly at Olympia earns immediate disapprobative notice.