Plural of cautionary; people who give or receive cautions or pledges; those who provide security or bonds.
From cautionary + -ies plural suffix. Cautionary comes from caution (from Latin cautio). Used in legal and historical contexts.
Scottish legal records from the 1600s are full of 'cautionaries'—people who literally stood up in court and pledged their money or property to guarantee someone else's behavior. You were putting your wealth where your mouth was.
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