Where the shape comes from
A body seen from the side, the belly drawn swollen and round — originally a pregnant body specifically, the fullest possible picture of embodiment, before the sense widened to the body in general and then to oneself, in person. It gives 身体, the body, and 本身, itself, in itself, and 单身, single, unattached, a body standing alone.
汉字 filed under 身
No published character on HSK Guide is filed under this radical yet. 汉字库.