玉蜀黍=옥수수 means maize, ((Amer)Indian) corn. Corn in the original meaning of any cereal would be 곡물 . . .
(It's literally jade (玉=옥 the Sinitic reading in Korean), 수수. 수수(속) is the Korean word for sorghum, used to make 부꾸미 ( https://en.wikipedia.org/wiki/Bukkumi ). It's from the modern Chinese (as it sounds to the Korean ear) reading for sorghum (aka (East-)Indian millet) which maize resembles somewhat. 수수 being literally Szechuan/Sichuan (蜀=수) millet (黍=수, which in Korean in the broad sense is 서곡) . . .)