This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
岇 combines 山 (mountain) with 卬, but the exact historical development and original meaning are uncertain.
A mountain 山 rising high above the base 卬 suggests something tall, but the exact meaning is unclear.
For ゴウ, imagine a mountain so tall it makes you say 'go!' as you start climbing: go -> ゴウ.