恰巧
qià qiǎo · HSK 7
by coincidence
🍀 恰 = exactly + 巧 = coincidental, so 恰巧 = exactly-by-coincidence
恰 carries the sense of just-right or precisely, and 巧 means coincidental or opportune. Together they stress that something lined up precisely by chance, which is why it reads as fortunately or by coincidence.
巧 — 工 (work) + 丂 (breath/exhalation phonetic)
巧 is a semantic-phonetic compound. The left 工 (work, craft) gives the meaning, pointing to skilled craftsmanship, while the right 丂 supplies the sound. From 'skilled handiwork' the meaning broadened to 'clever, ingenious,' and later to 'coincidental' as in 凑巧.