Voces mysticae are words not immediately recognizable as belonging to any known language, and are commonly associated with curse tablets. Anthropologist Stanely J. Tambiah proposed in 1968 that such words were intended to represent "the language that demons can understand".
Scholars from antiquity, like Christian philosopher Clement of Alexandria (ca. 200 C.E.), believed that human language was not appropriate for addressing the gods. Therefore, some of the inscriptions of these curse tablets are not easily translatable, because they were "invocations and secret names" which would only be understood by the spirits themselves. Another possibility is that curse tablets were produced by professionals who wished to lend their art a degree of mystique through the use of an apparently secret language that only they could understand. In support of this theory, at least some tablets appear to have blank spaces instead of a name for the target, suggesting they were prepared in advance, and that the desired target's name would be added on behalf of the customer.
Read more about this topic: Curse Tablet