watching someone secretly without their knowledge, or working as a secret agent to gather information for a country or organization.
From Old French 'espier,' meaning 'to watch or observe.' The word entered English in the 1300s and originally meant simple observation before taking on the modern sense of espionage and secret intelligence gathering.
Throughout history, spying has created its own vocabulary—'mole,' 'asset,' 'handler'—and spy agencies like the CIA actually hire linguists to track how language changes, because the words people use reveal what's happening in society.
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