This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development is uncertain. The modern form visually contains 蒿 on top and 禾 on the bottom, but this may not reflect the original composition.
The top 蒿 suggests a plant, and the bottom 禾 is grain. Imagine a tall grain plant used for straw or rough writing drafts, but the exact meaning is unclear.
For コウ, picture a tall stalk of grain (こう, 稿) being cut down: 稿 -> コウ, and the straw falls to the ground.