話し合う
はなしあう · hanashiau · JLPT N3 · verb-godan
to discuss
🗣️🤝 話し (talk) + 合う (meet, match) = talk until you meet in the middle
話し is the stem of 話す, to speak. 合う means to fit or come together, and as a suffix it makes the action mutual, the way 助け合う means to help each other. So the word is talking to each other until you reach agreement.
合 — 乛 (lid/roof) + 口 (mouth)
Originally a pictograph of a lidded vessel — a cover (亼) closing over an opening (口) — giving the core sense of 'come together, join, fit.' From 'fit/match' it extended to 'combine, unite, agree' and to measure-word uses. The reading hé reflects this 'joining' meaning.