To make something holy or sacred, or to show approval and good wishes toward someone.
From Old English 'bletsian' meaning 'to make blood,' possibly because blood was used in sacred rituals. The meaning shifted to 'consecrate' and then 'wish well' by the Middle Ages.
The word 'bless' traveled from religious ceremonies into everyday language—now people say 'bless you' after sneezing (thought to prevent the soul from escaping), showing how sacred words become casual habits.
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