abundance
穰 centers on plentifulness and rich yield, especially in the context of harvests. The core idea is abundance, with the given meaning "abundance" directly reflecting this sense of overflowing plenty.
穰 combines 禾 (grain) with 襄, which likely contributes the sound and carries a sense of fullness or abundance. The character is associated with rich harvests and plentiful grain.
The left side 禾 is grain, and the right side 襄 looks like a full, overflowing container. Picture a grain stalk so heavy with abundance that it bends under the weight.
For ジョウ, imagine a giant overflowing jar of grain: the jar is so full it's like a "joe" of abundance. Joe -> ジョウ.