lady's vanity case, trousseau
奩 centers on a container for a woman's personal items, specifically a vanity case or trousseau box.
奩 combines 大 (large) with 區 (box/container), suggesting a large box or case. The exact historical development is uncertain, but the component combination fits the meaning of a container for personal items.
A large (大) box (區) holds a lady's treasures: her vanity case or trousseau.
For レン, imagine a lady named Ren who carefully packs her vanity case: Ren -> レン, and the large box holds her precious items.