According to the book A Brief Introduction to Book Edition by Qu Wanli and Chang Peter, the explanation is as follows:
"During the Jiajing period, Zhu Jing carved hundreds of Tang poems, which can be proved. Later, in order to make it easier, catalpa gradually became a craftsman-style figure, which is now called Song-style figure. This font began in Longwan and became popular later.
Here are two examples: The Book of Southern Qi carved by imperial academy in the thirty-third year of Wanli and The Collection of Monks of Hong Xiuming carved by Jiguge in Shi Mao in the sixteenth year of Chongzhen. Although the printed version of Wanli and the printed version of Qizhen are similar in appearance, there is still a difference in Shen Feng, which requires something other than Zhu Mu Astragalus. "
Extended data
The culture of the Song Dynasty flourished, and the Song carvings were exquisite and atmospheric, which had high collection value. Scholars in the Ming Dynasty, especially bibliophiles, admired the "Song Block Edition", so the publishing circles in the Ming Dynasty often reprinted the Song Block Edition.
However, in order to facilitate and reduce the cost, these imitation Song editions of the Ming Dynasty often only engrave the word "Pikuo", instead of the rich Song style characters.
Finally, a font specially used for printing was formed. In the 12th year of Kangxi (A.D. 1673), it was stipulated in the preface of Jing 'an's "General Examination of Documents": "After that, when engraving books, all the styles are called Songti characters, and regular scripts are called soft texts". The name "Song Style" came from this.
References:
Baidu Encyclopedia-Song Ti