返答
へんとう · hentou · JLPT N1 · noun
answer
💬 返 = send back + 答 = answer: a reply is an answer sent back
返 means return or send back, and 答 means answer. Its close synonym 返事 (henji) also means reply, but 返答 is the more formal, written-style word.
答 — bamboo radical 竹 + 合 (combine)
Originally written with the bamboo radical because answers were inscribed on bamboo slips. The phonetic 合 ('to join, match') gives both the sound and the sense of a reply 'matching' a question. Over time 答 came to mean 'answer' or 'respond' generally.