How did the term causerie come to describe a short informal literary essay?

The term causerie originally referred to a friendly or informal conversation, derived from the French verb causer ("to chat").1

Its association with short, informal literary essays stems from the work of the French critic Charles Augustin Sainte-Beuve. Beginning in 1849, Sainte-Beuve published a weekly column in the newspaper Le Constitutionnel titled Causeries du lundi ("Monday chats"). Because these critical essays were written in a conversational, informal style, the title of his collection led to the word causerie acquiring its secondary meaning in English as a brief, informal essay or article.21