high, dangerous
岌 centers on a mountain that is both high and precarious: towering and dangerous. The two given meanings are tightly linked by the image of a steep, risky height.
岌 combines 山 (mountain) with 及, which likely contributes the sound and may suggest reaching or extending upward, giving the idea of a high, dangerous peak.
A mountain 山 with 及 underneath looks like a peak that reaches dangerously high. Picture a climber barely hanging on to a steep, towering cliff.
For キュウ, imagine a climber on this high, dangerous mountain letting out a sharp 'kyu!' sound as they slip: kyu -> キュウ.
tall (as a mountain, etc.)