This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
歰 is a rare character composed of two 刃 (blade) elements side by side. The exact historical development and original meaning are uncertain.
Two blades 刃 placed side by side suggest something related to cutting or sharpness, but the exact meaning is unclear. Think of it as a double-edged mystery.
For シュウ, imagine two blades clashing with a sharp 'shu' sound: shu -> シュウ, as the twin blades meet.