This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 峉 is uncertain. It combines 山 (mountain) with 各, but the original meaning and component relationship are unclear.
With 山 (mountain) above 各 (each), picture each mountain having its own distinct shape, but the meaning remains uncertain.
For ガク, imagine a mountain climber reaching the peak and exclaiming 'Gak!' in surprise at the view: Gak -> ガク.
—