baby, infant
囝 centers on a very young child: a baby or infant.
囝 combines the enclosure 囗 with 子 (child), suggesting a child kept within a protected space. The exact historical development is uncertain.
A child 子 is kept safe inside an enclosure 囗, like a baby in a crib. 囝 is a baby or infant.
For ケン, imagine a baby named Ken inside the enclosure: Ken -> ケン, and the child is the baby 囝.