往返
wǎng fǎn · HSK 7
to go back and forth
🔁 往 = go toward + 返 = return; together: go and come back, a round trip
往 means to head toward somewhere; 返 means to turn back. Stack them and you get the full out-and-back motion of a round trip, going there and returning.
往 — 彳 (step radical) + 主 (phonetic)
往 originally depicted a foot moving toward a place, with the 彳 radical signaling motion or walking. The right component 主 served mainly as a phonetic clue. Over time the meaning settled into 'to go (toward)' and, by extension, 'past' or 'previously'.