Fangyan.

About Fangyan

The Fangyan is a Chinese dictionary compiled in the early 1st century CE by the poet and philosopher Yang Xiong. It was the first Chinese dictionary to include significant regional vocabulary, and is considered the "most significant lexicographic work" of its era. His dictionary's preface explains how he spent 27 years amassing and collating the dictionary. Yang collected regionalisms from many sources, particularly the 'light carriage' surveys made during the Zhou and Qin dynasties, where imperial emissaries were sent into the countryside annually to record folk songs and idioms from across China, reaching as far north as Korea.