This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
蠰 combines 虫 (insect) with 襄, which likely contributes a phonetic element. The exact historical development is uncertain.
The left side 虫 suggests an insect, and the right side 襄 is a complex shape. Picture a rare, long-horned beetle (かみきりむし) with elaborate antennae that match the intricate strokes of 襄.
For ショウ, imagine a showy beetle with long antennae: show -> ショウ, and the insect 虫 is the star of the show.