Two sources: a humble clerk correcting Li Xiang's mispronunciation of a 《
春秋》 character (《
唐摭言》), and the poet Qi Ji changing
数枝开 to
一枝开 on Zheng Gu's suggestion — the single edit turned a 'plum in bloom' into an 'early plum.' Zheng Gu was thereafter called
一字师.