本身
běnshēn · HSK 6
self
本 = root/origin + 身 = body/self → the thing itself
本 means root or origin (a tree 木 with a mark at its base). 身 means body or self. Together: the root-body, i.e. the entity itself, as opposed to something derived from it.
本 — tree 木 + mark at base
本 is a pictograph of a tree (木) with a stroke at its base, marking the roots. From this 'root' meaning it extended to 'origin,' 'source,' and 'foundation.' In modern usage it also serves as a measure word for bound objects like books.
身 — pictograph of a pregnant body
身 is a pictograph originally depicting a person with a swollen belly, representing a pregnant woman in profile. Over time the meaning broadened from 'pregnancy' or 'torso' to refer to the body in general, and by extension oneself or one's person.