お子さん
おこさん · okosan · JLPT N4 · noun
child
👶 お子さん = honorific o + ko (child) + san: Mr./Ms. Child, so never your own
Three parts: polite prefix お, 子 (ko, child), and the respectful suffix さん. Japanese honorifics point outward, so you only wrap someone else's child in them. Your own child is plain 子ども or うちの子.
子 — pictograph of a baby/child with arms out
子 began as a pictograph of a swaddled infant with a large head and outstretched arms, originally meaning 'baby' or 'child.' From there it broadened to 'son,' 'offspring,' and a respectful suffix for masters like 孔子 (Confucius). It also became one of the twelve earthly branches.