chick, fledging, infant, toddler
鶵 centers on a very young bird or child: a chick, fledgling, infant, or toddler. The idea is small, dependent, and newly hatched or born.
鶵 combines 芻 (likely phonetic, with a meaning related to grass or cutting) and 鳥 (bird), suggesting a young bird. The exact historical development is uncertain, but the phono-semantic structure is plausible.
The left side 芻 looks like cut grass, and the right side 鳥 is a bird. Imagine a tiny chick hiding in freshly cut grass, too young to fly.
For スウ, picture a tiny chick making a soft 'sue' sound as it peeps from the grass: sue -> スウ.
mythical Chinese bird similar to the Chinese phoenix