to store up, to pile up
𠂤 centers on accumulation: storing things up or piling them together. The two given meanings are direct expressions of this idea.
The historical origin of 𠂤 is uncertain. It may have depicted a mound or pile, consistent with its meanings of storing and piling up, but the exact development is unclear.
The shape resembles a container with something piled inside. Picture a storage jar being filled and piled high with goods.
For タイ, imagine tying up a pile of goods with a rope: tie -> タイ, and the pile is stored securely.