lofty
巃 centers on towering height, especially of mountains or terrain: something steep, lofty, and imposing.
巃 combines 山 (mountain) with 龍 (dragon), likely to evoke the image of a dragon-like towering mountain. The exact historical development is uncertain, but the semantic link between mountains and loftiness is clear.
A mountain 山 with a dragon 龍 coiled on top: the dragon's towering form makes the peak even more lofty and steep.
For ロウ, imagine a low mountain that suddenly grows into a lofty peak: low -> ロウ, but the mountain becomes the opposite of low.