The origin and evolution of the word "底"

The Chinese character 底(di),used as a pronoun and an auxiliary word in modern times,was first found in the literature of the Wei and Jin Dynasties,and widely used during the Tang and Five Dynasties.It was also common in the poems in the period of Song.However,during and after the Yuan and Ming Dynasties,this character used as a pronoun became extremely rare,and meanwhile the word used as an auxiliary word was replaced by another character 的.The present paper is to summarize the study of this case in the history of Chinese language and give a initial view by analyzing the pronunciation change of it.