Done and Dusted

Did you ever catch yourself saying something and wondering  "where on earth did that come from? "

When I finish a call for a customer I often say "that's it done and dusted!" 

The expression is mostly used in British English in informal contexts to mean to successfully complete something. When a businessman says that a deal has been done and dusted, he means that he has been successful in clinching it; there is nothing left to be done.

The expression comes from the world of writing. In the past, everyone made use of ink to write; people dipped their quill or pen into a bottle of ink before putting words on paper. Those of us who have used a fountain pen know that ink doesn’t dry very quickly. Sometimes, you had to wait for a long time before the paper absorbed the ink. To quicken the drying process, people used to sprinkle an absorbent dust or powder on the paper. Once the ink had dried, the powder was dusted off the paper.

In the words attributed to Michael Caine, "not a lotta people know that!"