volume, product (x*y), acreage, contents, pile up, stack, load, amass
積 centers on accumulation: piling things up, stacking, loading, or amassing. The mathematical and spatial senses (volume, product, acreage, contents) are natural extensions of this idea of gathered quantity.
積 combines 禾 (grain) with 責, which likely contributes the sound and the idea of piling or accumulating. The original sense may have been gathering harvested grain into stacks.
Grain 禾 piled up under a roof-like 責 shape: imagine a barn filled with stacked sacks of rice, accumulating volume and weight.
For セキ, picture a stack of grain so high it blocks the sun, creating a shadowy 'seki' (セキ) corner. The piled-up grain casts a dark seki-shaped shadow.
intention; plan; purpose; expectation
active; positive; progressive
to pile up; to stack
area (measurement); square measure; size (of land); floor space
accumulation; accumulate; store
pile; accumulation
accumulation
estimate; estimation; valuation; quotation
to pile up; to accumulate
product
fallen snow; snow cover
loading; carrying
accumulation
capacity; volume
saving; savings; accumulation; putting aside; reserving
accumulation; pile; heap
capacity; volume
addition; adding up
piling up; accumulating; forming a (huge) pile; lying in piles
to pile up; to accumulate
loading on top; piling on top; upper load; goods loaded on top; deck cargo
to load (with goods, cargo); to put on board; to stow aboard
(price) quotation; quote
planted area