老生常谈（老生常談）　

◎ 老生常谈 lǎoshēng-chángtán

[be trite and commonplace;common talk of an old scholar;commonplace;platitude; standing dish; sunday schools truth; twice-told tale] 原义为年老书生的平凡议论,泛指经常说起的老话

邓颺怒曰:“此老生之常谈耳!” 辂曰:“老生者见不生,常谈者见不谈。”——《三国演义》