noun
studying the past; researching history
Archaic standalone noun; in modern Japanese it is almost exclusively used inside the four-character idiom 温故知新 (おんこちしん, 'learning from the past').
See also: 温故知新
「温故知新」の「温故」は、古いことをよく調べて学ぶという意味です。
The 温故 in 温故知新 means to study and learn from old things.
温故 is the archaic noun meaning 'studying the past'; 温故知新 is the common modern idiom meaning 'learning from the past to gain new insights'.
Derived from the Chinese idiom 温故知新 (wēn gù zhī xīn), from the Analects of Confucius. The exact historical derivation of the standalone noun 温故 is uncertain; it is now archaic outside the full idiom.