巣
ソウ, す, す.くう

nest, rookery, hive, cobweb, den

JLPT1 G4 S11 F1588

The relevant seal inscription form shows chicks in a *nest* high in a tree (compare 喿 as described in 操) → *build a nest*; *lair*; *den*; (spider's) *web* → *hotbed*.

[Full Kanji Etymology List]