移行
いこう · ikou · JLPT N1 · noun
switching over to
移 (shift) + 行 (go) = going across from one system or state to another
移 means shift or transfer, and 行 means go, so 移行 is moving over to a new setup. It is used for software versions, schedules, and transitions between periods.
移 — grain 禾 + many 多
Originally a semantic-phonetic compound: 禾 (grain) gives the meaning and 多 (duō) suggested the sound in Old Chinese. It first referred to transplanting rice seedlings, then broadened to mean 'to move, shift, or relocate' in general.
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.