On fire or burning brightly; also means glowing or shining intensely with light or color.
From 'a-' (on) + 'blaze' (fire, flame), where 'blaze' comes from Old English 'blæse' (torch, fire). The compound formed in Middle English.
The word 'ablaze' has an interesting metaphorical life in English—we say emotions are 'ablaze,' passion is 'ablaze,' eyes are 'ablaze'—transferring the intensity of fire to feelings and expressions.
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