以後
いご · igo · JLPT N2 · noun
from now on
🕰️ igo sounds like I go: from now on, I go my own way
以 marks a starting point (from) and 後 means after or behind, so 以後 is from this point and after. Compare 以前 (いぜん, before this), which swaps 後 for 前 (front).
以 — phonetic 㠯 (plow/tool) + 人 (person)
Originally a pictograph of a hand-held plow or tool (㠯), later combined with 人 (person) to suggest 'using' something. The core meaning 'to use' extended metaphorically to 'by means of', 'with', and 'because of'. In modern Chinese it functions mainly as a grammatical particle.