tanned leather
鞣 centers on the process of treating animal hide to make it durable and flexible: tanned leather.
鞣 combines 革 (leather, hide) with 柔 (soft, gentle), suggesting the process of softening hide into leather. The exact historical development is uncertain, but the component relationship is consistent with the meaning.
Leather (革) is made soft and flexible (柔) through tanning. Picture a stiff hide being worked until it becomes supple tanned leather.
For ジュウ, imagine a tanner saying 'Jew, you want this fine leather?' The word 'Jew' cues ジュウ, and the scene ties to the leather trade.