Studying To Hoai's memoir, we can not only see that the author was a writer with an abundant and profound language knowledge, flexible and talented use of national language to describe, tell, and look back what he has experienced, but also discover his creativity and rule-break in word formation when producing his writing works. A number of words were created by combining, separating, or forming different words or meanings by himself to express the content of the events he wanted to manifest in the most effective way. This confirms not only his personal experience and his rich language knowledge but also his great contribution to the development of the Vietnamese language in the 20th century.