Rav Yisrael Meir Kagen, the Chofetz Chaim
R’ Yisrael Salanter once spoke in Vilna about the severity of the sin of loshon hora, and proclaimed, “Would that some chochom would write a sefer about the laws of loshon hora.”  R’ Yisrael Meir heard the words and undertook the task of writing the book, which he called Chofetz Chaim.
From Sparks of Mussar by R Chaim Ephraim Zaitchik