Aklo: The tongue of the ancient serpent folk of Valusia in the Cthulhu mythos, this is the ritual language discussed in most translations of the Necronomicon. It was mentioned in the original Lovecraft Circle’s tales inn several places, including The Dunwich Horror, as with the incantations of the half-human Wilbur Whateley and his sorcerer grandfather, named in some places Noah Whateley of simply Old Whateley. It was the language originally used by Old Whateley to call Yog-Sothoth to Earth to father Wilbur and his twin brother, and to destroy or banish the latter.
Aramaic: Often called the “language of Christ,” it’s been steeped in mysticism within the last few decades thanks to its close association with the Son of God. After all, the word Thaumaturgy comes from “thaumturge” which means “wonder worker” (wonders aka miracles).
Enochian: Enochian was pretty much invented by John Dee and Edward Kelley, but if their claims are true then the language might be especially potent in a magical sense because it was handed down from on high. Sometimes called Angelical or Adamic, it’s the language that was spoken in the garden of Eden. It uses the same constructions as English (apparently) and a font for game handouts can be found here.
Etruscan: Etruscan is the language of the eponymous ancient peoples of western Italy, it influenced Latin early on and might be considered a precursor of that language. Interestingly enough, the Etruscans had a belief system that was part ancestor worship, part polytheism, and relied on a system of seers and haruspices (those who divine through entrails). It might be perfect for magics that divine the future.
Pali: Pali is a dead language known for being the language many of the earliest Buddhist scriptures are written in. If that doesn’t draw you in that I don’t know what can. Think about it. This long-dead tongue which one of the most interesting religion’s earliest texts are written in. Check out this online dictionary here.
Sankrit: Is another dead language that is still studied today because of so many texts written in it – especially the Rigveda. Those who study Kalaripayit (GURPS Martial Arts, p. 168) might learn secret mantras (spells) whose source of power may lay in it’s link to this ancient tongue.
Sumerian: Another oldie but goodie (please don’t hit me for that pun), you can’t go wrong with magic’s language being one of the first tongues spoken by man (that was recorded at least).
Picking Over the Bones
My list might work just fine for campaigns based on Earth – but what about those taking place on other planets or far into the future? Tolkien created his own language by distilling aspects of Middle English and various other tongues. Ambitious GMs could do the same. In the past I’ve used Holly Lisle’s “Create a Language Clinic,” which I highly recommend to any worldbuilder, GM, or author – it’s quite useful. In the end, even a veneer of the strange and exotic might be enough – just don’t add too many apostrophes or dashes…