A file, "file," is usually a place where you put business documents that are related to each other.  一个文件夹，“文件夹”通常是放置相关业务文档的地方。

Circular, "circular," means round. The expression, circular file, refers to a wastebasket or a trash basket,  环形，“环形”的意思是圆。这个表达，回收箱，指的是一个废纸篓或垃圾桶，

a place where you would get rid of something - throw something away.  在这里，你可以丢掉一些东西——把它们扔掉。

So, someone may say, "Well, I'm going to put this in my circular file, " that is I'm going to throw it away.  所以，有人可能会说，“好吧，我要把这个放在我的回收箱里，”就是说我要把它扔掉。

Of course, it's not really a file. If it were a file, you would keep it in a filing cabinet.  当然，这不是一个真正的文件。如果它是一个真正的文件，你会把它放在文件柜里。

I worked at a job, many years ago, where I had a small cubicle and we had lots of paperwork. 很多年前，我工作的地方有很多小隔间，当时我们有很多文书工作要做。

Many times, we would joke about putting some of the sales paperwork into the circular file because it was more work for us to have to read it. 很多时候，我们会开玩笑地说，把一些销售文件放入回收箱中，因为还有很多内容等着我们去阅读。