子息
しそく · shisoku · JLPT N1 · noun
son
子 = child + 息 = breath: the child who carries the family's breath forward
Honorific for another person's son (ご子息). 息 originally meant breath, and by extension life passed on to descendants. For your own son, everyday speech uses 息子.
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.