温故知新：おんこちしん [on-ko-chi-shin]

前に学んだことや昔の事柄をもう一度調べたり考えたりして、新たな道理や知識を見い出し自分のものとすること。古いものをたずね求めて新しい事柄を知る意から。

And to think or examine the thing and the old things that learned before once again , be a mine found a new reason and knowledge . From intent to know the new things seeking asked the old one.