save, hoard
攢 centers on gathering and keeping things together, especially for future use: saving up or hoarding resources.
攢 combines 扌 (hand) with 贊, which likely contributes both sound and the idea of gathering or accumulating. The exact historical development is uncertain.
The hand radical 扌 beside 贊 suggests a hand gathering things together. Picture a hand carefully piling up coins or supplies to save and hoard.
For サン, imagine a hand saving up sand (サン) in a pile: sand -> サン, and the hand hoards every grain.