'aglow' originates from the prefix 'a-' meaning 'in' or 'on' and the word 'glow', which comes from Old English 'glōwan', meaning 'to shine'.

'glōwan' transformed into the Middle English word 'glowen', and eventually became the modern English word 'glow', with 'aglow' forming as a compound.

Initially, it meant 'to shine or emit light', and this meaning has largely remained the same in modern usage.