椅子
いす · isu · JLPT N5 · noun
chair
🪑 椅子 = chair (椅) + small-thing suffix (子); isu: is u sitting?
椅 carries the wood radical 木, since chairs were wooden, plus 奇 for sound. 子 is a noun ending borrowed from Chinese, also found in 帽子 (hat) and 菓子 (sweets). Sound hook: isu = is u sitting? Then you need a chair.
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.