This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
翨 combines 羽 (feathers) with 是, but the exact historical development and original meaning are uncertain.
Feathers 羽 over 是 suggest a bird or something related to flight, but the exact meaning is unclear.
For シ, imagine a rare bird with feathers 羽 that makes a soft 'shee' sound: shee -> シ.