Oracle-bone and bronze forms show the side view of a person with the abdomen deliberately enlarged or marked, sometimes with a dot like a navel. The earliest meaning was probably the belly or trunk; the character later widened to the whole body and to oneself. This sketch keeps the human outline, rounded abdomen and small navel mark found in early forms.
A piece of culture
Your body, yourself 身 can point to the physical body and also to the self. In 身体 / 身體, shēntǐ in Mandarin and san1 tai2 in Cantonese, it means “body”. You will also meet it in 身份, shēnfèn / san1 fan6, meaning a person’s identity or status. One ancient body-shape still helps Chinese talk about who you are.