This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development is uncertain. The modern form combines 艹 (grass) with 戢, but the original semantic and phonetic roles are unclear.
The grass top 艹 over the complex lower shape 戢 suggests a plant, but the specific meaning is unclear.
For シュウ, imagine a rare plant named 'shu' growing among the grass: shu -> シュウ.