finishing touch / stroke

What is the origin of the idiom "finishing touch" and when to use it?

The phrase "finishing stroke" has its roots in the sport of fencing, which dates back to the 16th century. In fencing, two opponents use swords to score points by touching their opponent with the tip of their sword. The final, decisive move that scores the winning point is known as the "coup de grâce" or "the finishing touch." Over time, the term has come to be used more broadly to describe any final, decisive action or step needed to complete or perfect a task or project.