Revealing or indicating something, especially something meant to be kept secret; a person who reveals secrets or private information.
From Middle English, compound of 'tell' + 'tale'. Originally referred to someone who tells tales or stories, evolving by the 16th century to mean someone who reveals secrets or betrays confidences.
The word beautifully captures the dual nature of information - the same qualities that make someone a good storyteller can make them a dangerous keeper of secrets. In nautical contexts, a 'telltale' is also a device that shows wind direction, maintaining the theme of revelation.
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