Lingo
tell on
to give away information one has obtained about someone, particularly to someone in authority
The idiom "tell on" is derived from the literal meaning of the words. To "tell on" someone means to report their actions or misdeeds to an authority figure or someone in a position of control or responsibility. Its origin is likely rooted in the natural human tendency to inform others about wrongdoing or suspicious behavior, particularly when it affects one's well-being or interests. It is frequently used in the context of children reporting on their peers or siblings, but it can apply to people of all ages.
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