Quiz: Remember the definition of mal de mer?
late 15c., "sign, portent, something extraordinary from which omens are drawn," from Latin prodigium "prophetic sign, omen, portent, prodigy," from pro- "forth" (see pro-) + -igium, a suffix or word of unknown origin, perhaps from *agi-, root of aio "I say" (see adage). Meaning "child with exceptional abilities" first recorded 1650s.
a child who, by about age 10, performs at the level of a highly trained adult in a particular sphere of activity or knowledge. In this sense, neither high intelligence nor eccentric skills by themselves qualify a child as a prodigy. Rather, it is the capacity to perform in a recognized area of endeavour in such a way as to receive broad acclaim that defines the prodigy. Therefore, individuals who are chess prodigies or "lightning calculators" (those who have a remarkable memory for figures) but who are otherwise mentally or developmentally disabled (such as "idiot savants") are not prodigies.