Upper trigram
☶
Mountain · Gen
Stillness and limit.
FamilyYoungest son
ElementEarth
Hexagram 23 of 64
☶☷ Splitting Apart
Decay from below; do not resist, wait.
Lower trigram
☷
Earth · Kun
Receptive yielding.
FamilyMother
ElementEarth
The image
Mountain above, Earth below.
Mountain over Earth: stillness and limit meeting receptive yielding.
That combination is the whole meaning of hexagram 23. Nothing about it is arbitrary — change either trigram and you get a different hexagram with a different reading, which is why the 64 form a system rather than a list.