Can you give a specific example? The term “anamorphic encryption” was used in a paper from EUROCRYPT 2022 and I don’t see any prior formal study of the subject. A follow-up paper from PoPETS 2023 establishes that most of the widely-used cryptosystems introduced over the past few decades are indeed capable of anamorphism but nobody used the term “anamorphic encryption” until the last few years.

To say that they have been used for “hundreds” of years seems like a sweeping generalization in need of better context.