ジ, ニ, ゲイ, こ, こ, っこ, る
newborn babe, child, young of animals
JLPT2 G4 S7 F679
The relevant seal inscription form shows, as depicted in 思, a profusion of fine bones in fontanels (open spaces in an infant's skull over which the skull bones eventually fuse) + 儿 person → *infant*; (very young) *child*.
[Full Kanji Etymology List]