Слово "idiom". Англо-русский словарь Мюллера

He paused before saying "mama" because what he meant to say was "tu chingada madre", an idiom used as a disrespectful allusion to the other party's mother.

The will of Switzerland to be united, despite the diversity of its idioms, is a fact of far greater importance than a similarity of language often obtained by vexatious methods.