This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
嶫 combines 山 (mountain) with 業, but the exact historical development is uncertain. It may be a variant or specialized form related to mountain peaks or lofty heights.
The left side 山 means mountain, and the right side 業 suggests work or business. Imagine a mountain so high that climbing it is a serious undertaking.
For ギョウ, picture a mountain guide named Gyou leading a group up the steep slope: Gyou -> ギョウ, and the mountain looms ahead.