The term "Rosetta Stone" is often associated with the artifact discovered by Napoleon's army in 1799 that helped decipher Egyptian hieroglyphs. However, there are several synonyms that can be used in place of this term. One common synonym is "language key," which refers to any tool or resource used to decipher or translate a language. Another is "cipher guide," which is similar but specifically refers to decoding a code or cipher. Additionally, "key to understanding" or "clue to interpretation" can also be used when referring to a text or artifact that provides crucial information for understanding a language or culture.