He wrote a memorandum to remind himself of tomorrow's meeting.

memorandum 来自拉丁语，原意是"需要记住的东西"。这个词由 memory（记忆）的词根 memor- 和表示"事物"的后缀 -andum 组成，指"备忘的记录或文件"，通常缩写为 memo。