box, basket
簏 centers on a container made of bamboo: a box or basket used for holding items.
簏 combines 竹 (bamboo) and 鹿 (deer), likely as a phono-semantic compound where 鹿 contributes the sound and 竹 indicates a bamboo container.
Bamboo 竹 on top of a deer 鹿: imagine weaving a bamboo basket to carry deer-shaped offerings, making it a sturdy box.
For ロク, picture a lock on the bamboo box: lock -> ロク, keeping the basket securely closed.