1590s, "noble in nature," from Latin ingenuus "with the virtues of freeborn people, of noble character, frank, upright, candid," originally "native, freeborn," from in- "in" (see in-(2)) + gen-, root of gignere "beget, produce" (see genus). Sense of "artless, innocent" is 1670s, via evolution from "high-minded" to "honorably open, straightforward," to "innocently frank." Related: Ingenuously; ingenuousness.