流行る
はやる · hayaru · JLPT N3 · verb-godan
to come into fashion
👗 流行る = flow + go: a trend flows and goes everywhere; hayaru ~ hayai (fast)
The kanji 流 (flow) + 行 (go) describe something spreading through society like a current. The reading hayaru shares its root with hayai (fast): a fad is something that catches on quickly. The noun 流行 (ryūkō) means fashion or trend.
流 — water radical 氵 + 㐬 (phonetic, child being born)
流 is a semantic-phonetic compound. The water radical 氵 gives the meaning, while 㐬 depicts an infant being born head-down with amniotic fluid, suggesting downward flow. Together they convey water flowing, and by extension 'to flow' or 'current'.
行 — crossroads pictograph (left 彳 + right 亍)
行 originally pictured a four-way crossroads in oracle bone script, with two paths meeting. From 'road' it extended to 'walk, go, travel,' and then to 'a row, line' or 'business firm' (read háng). The two halves 彳 and 亍 are the split sides of that ancient crossroads.