交互
こうご · kougo · JLPT N1 · na-adj
alternate
🤝 交 = exchange + 互 = each other, so 交互 = exchanging with each other = mutual
互 means each other, as in 相互 (mutual). 交 means exchange or cross. Together they describe things passing back and forth, or taking turns (alternate).
交 — top 亠 + 父-like crossed legs
Originally a pictograph of a person standing with legs crossed, showing the idea of crossing or intersecting. From this concrete image, the meaning extended to abstract senses like 'exchange,' 'interact,' and 'hand over.' Modern uses such as 交流 (exchange) and 交通 (traffic) all trace back to this core notion of crossing.