noun
vast knowledge; deep erudition; store of expertise
Often used when someone shows off or shares detailed knowledge on a niche topic. Can carry a slightly pedantic or enthusiastic tone.
彼は歴史についてうんちくを語り始めた。
He started sharing his vast knowledge about history.
うんちくを傾けるのが彼の趣味だ。
Showing off his extensive knowledge is his hobby.
Original kanji form, now uncommon. 蘊 means 'accumulate' and 蓄 means 'store up'.
Search-only mixed kanji-kana form; not a standard spelling.
From Chinese 蘊蓄 (yùnxù), meaning 'to accumulate and store'. The Japanese reading うんちく is the on'yomi. The word originally referred to storing up knowledge, and later came to mean the deep knowledge itself.