This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The historical origin of 幑 is uncertain. It visually contains 彳, 山, 帀, and 攵, but the exact development is unclear.
With no clear meaning, focus on the shape: a person 彳 under a mountain 山, with a cloth 巾 and an action 攵. Imagine a lost traveler marking a trail with cloth.
For キ, picture a key tied to a cloth marker: key -> キ, and the cloth marks the spot.