matter, material, substance
貭 centers on the fundamental stuff of things: matter, material, or substance. It points to what something is made of at its core.
貭 is a variant form of 質. The standard form 質 combines 貝 (shell, value) with 斦 (which likely contributes sound), expressing the idea of substance or material worth. The variant 貭 replaces the upper part with 十, but the exact historical development of this variant is uncertain.
Ten 十 shells 貝 piled up represent the raw material or substance of value: the fundamental matter of trade.
For シツ, imagine a sheet of material: sheet -> シツ, and the ten shells on the sheet are the substance of the trade.