The most likely to change your mind or loyalties without reason; most unreliable or unpredictable in behavior.
From Middle English 'fikel,' possibly from Old English 'ficol' meaning 'deceitful.' The superlative 'ficklest' adds the -est suffix to 'fickle,' which originally referred to moral weakness or untrustworthiness, later extending to any unstable behavior.
Medieval people used 'fickle' to describe unreliable traitors and false friends—it was basically their way of calling someone untrustworthy! The word stuck around because human nature hasn't changed; we still struggle with people who flip-flop on their promises.
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