non-glutinous (ordinary) rice
秔 centers on a specific type of rice: non-glutinous, ordinary rice, as opposed to sticky or glutinous varieties.
秔 combines 禾 (grain/rice plant) with 亢, which likely contributes the sound. The character was used specifically for non-glutinous rice.
The grain radical 禾 beside 亢 (which looks a bit like a tall, straight stalk) represents ordinary, non-sticky rice that stands upright in the field.
For コウ, imagine a field of ordinary rice being harvested by a farmer named Kou: Kou -> コウ, and he gathers the non-glutinous grain.