telltale (n.)youdaoicibaDictYouDict[telltale 词源字典]
also tell-tale, "discloser of secrets," 1540s, from tell (v.) + tale. As an adjective from 1590s. Phrase tell a tale "relate a false or exaggerated story" is from late 13c.[telltale etymology, telltale origin, 英语词源]