③
寻常事;老生常谈(人所共知的老话)
相关 名词理据由「平凡」之形容词转指「平凡之语、人之常说」——寻常性凝作通用常谈。
例句
Their talk was full of commonplaces.他们交谈里满是老生常谈;承本义「寻常」——人云亦云的常谈。The speech opened with the usual commonplaces about unity.演讲开头是些关于团结的老生常谈;同此——通行之套话。
溯源路径本义 → 义项3