forsooth

In 2002, I asked Merriam-Webster the following question. Emily Brewster replied as follows.

Q: How can “forsooth,” which means “in truth,” “imply doubt”?

A: “Forsooth,” like “indeed,” can imply contempt or doubt when it’s used, as it often is, with sarcasm. It’s similar to the more modern and direct “I don’t think so,” as in, “You called but no one answered? I don’t think so.” One might also say, “You called but no one answered, forsooth.”