The title was taken from a sentence in the diary: "When I think upon these fleeting things, I feel I do not even know if they really existed or not, and thus have named my diary the Kagero (gossamer) Diary."
題名は日記のなかの文「なほものはかなきを思へば、あるかなきかの心ちするかげろふの日記といふべし」より。