a type of millet
秬 refers to a specific type of millet, a grain crop. Its meaning is narrow and concrete, centered on this particular plant.
秬 combines the grain radical 禾 with the phonetic component 巨, which likely indicates the sound. The character was created to name a specific type of millet.
The grain plant radical 禾 beside the large 巨 suggests a notably large or robust type of millet. Picture a giant stalk of millet towering over the field.
For キョ, imagine a giant millet plant so big it casts a shadow over a Kyoto garden: Kyoto -> キョ, and the huge millet is the centerpiece.