Making a high-pitched, sharp sound; also slang for informing on someone to authorities.
From Middle English 'squeken,' of imitative origin, imitating the actual sound. The slang sense emerged in the 1800s from the squeaky sounds of shoes worn by spies.
The criminal slang 'squeaker' for an informant likely came from shoes squeaking and giving away someone's hiding spot—or from rats squeaking, another symbol of betrayal and pest-like informants.
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