Coleridge found the source of "our pseudo-poetic diction" in Pope's Homer.
1520s, from poet + -ic, or else from or influenced by Middle French poetique (c.1400), from Latin poeticus, from Greek poietikos "pertaining to poetry," literally "creative, productive," from poietos "made," verbal adjective of poiein "to make" (see poet). Related: Poetics (1727). Poetic justice "ideal justice as portrayed in plays and stories" is from 1670s. Poetic license attested by 1733.
Earlier adjective was poetical (late 14c.); also obsolete poetly (mid-15c.). Related: Poetically (early 15c.).