telltale
UK: ˈtelteɪl | US: ˈtɛlˌteɪl
n. 1. A person who reveals secrets or private information; an informer.
n. 2. A sign or indicator that reveals or suggests something (e.g., "a telltale blush").
adj. Serving to reveal or betray something (e.g., "telltale evidence").
The word "telltale" combines the verb "tell" (from Old English tellan, meaning "to recount or narrate") and the noun "tale" (from Old English talu, meaning "story or account"). Originally used in Middle English, it literally meant "one who tells tales." Over time, it evolved to describe someone who reveals secrets (often pejoratively) or an object/sign that inadvertently discloses information. The logic is straightforward: a "teller of tales" becomes a revealer of hidden truths.
The child was labeled a telltale after reporting the mischief to the teacher.
The cracked window was a telltale sign of the burglary.
Her nervous glance was a telltale giveaway of her guilt.
The engine’s smoke acted as a telltale of mechanical failure.
He despised office telltales who spread gossip.