投身
toú shēn · HSK 7
to throw oneself into sth
🤿 投 throw + 身 body/self = throw your body/self into something
投 is the throw/cast component (as in 投票 to cast a vote); 身 means body or self. Together they literally read throw-self, so 投身 is to throw oneself into a cause or career.
投 — hand radical 扌 + weapon 殳
Originally a pictograph of a hand (扌) throwing or hurling a weapon or staff (殳). The core meaning 'to throw, cast, hurl' extended over time to figurative senses like 'to invest,' 'to deliver,' or 'to throw oneself into' something.
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.