螢雪之功 (Yíng xuě zhī gōng) ( 형설지공 in Korean ). An interpretation of the four character idiom is achievement by firefly and snow. It is a reference to two Chinese classical stories in which poor children without the means for candles or lamps of some kind, study diligently in their absence. The stories are said to have originated in the Jin Dynasty. One story is that a prominent scholar Che Yin as a poor child gathered fireflies in a cloth bag and studied by their light.