Present participle of leak; allowing liquid, gas, or information to escape through an opening or breach.
From Middle Dutch 'leken' meaning 'to drip' or 'to let water in'. The word entered English in the 15th century, initially for liquids, with the metaphorical sense of information 'leaking' developing in the 20th century.
The metaphorical use of 'leaking' for secret information is brilliant - it captures how sensitive data seeps out through small cracks in security just like water through a tiny hole in a container!
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