One picture holds the whole word: a thing with flames coming off it, burning where everyone can see. Hold that picture and the other uses fall out of it. Leaves can be so red that the tree looks like it is burning. A person can be so that something inside seems to burn. The fire is real in the first use and borrowed in the others, but the look is the same every time: hot, bright, impossible to miss.
From the word’s history
Aflame comes from Middle English a-flame: the old prefix a- meaning 'on / in the state of' plus flame (from Old French flame, Latin flamma). The literal sense is 'in flames', which is exactly the picture the modern word still carries, and it explains why aflame behaves like asleep and awake in a sentence.
aflame 來自中古英語的 a-flame。a- 是一個老的字首，意思接近「處在⋯⋯的狀態」；flame 是火焰，經古法文 flame 來自拉丁文 flamma。字面就是「在火焰之中」，跟今天的核心畫面完全對得上，也說明了它為什麼跟 asleep、awake 一樣習慣放在 be 動詞後面。
Wiktionary etymology supplied in this evidence packet (kaikki:3f6f69a190036ae4:506261444:11227): Middle English a-flame < a- + flame/flaume/flawme < Anglo-Norman flaume < Old French flame < Latin flamma.
登入就可以看每一支怎麼連回核心畫面。