I couldn't say what the process was called at the time, but I see it listed as "peek-a-boo" or "cut away" in a number of examples. I believe the earliest I have seen it listed as "peek-a-boo" is in a book by the Smithsionian from the 1970's that studied 13-star flags in the Revolution and beyond. There are a least of few examples of this being done as far back as the Revolution, and I wouldn't be surprised if it went back even farther still. I would love to see a period source that lists their name for the process.

Josh Bucchioni