The first language, according to Herodotus.
Anthologica Universe Atlas / Reference / Natlangs / Indo-European / Graeco-Phrygian / Phrygian

Phrygian was a language spoken in Asia Minor in the early classical era, closely related to Greek. Although it is scarcely attested, we have a general idea of what the language looked like and how it developed. There were two "stages" of Phrygian, "Paleo-Phrygian" from about 800 BC and "Neo-Phrygian" in the late Hellenistic and Roman era, but for convenience they are usually treated as close varieties of the same language. Following is a five-minute description of the language.

-Phrygian was closely related to Greek (they are considered to be in a "Graeco-Phrygian" branch of Indo-European by many linguists), and exhibits some striking similarities. PIE *o is maintained as a separate vowel from *a, the palatovelars merged with the plain velars, word-final *m became /n/, past tense forms exhibit an augment (Phrygian eberet "he carried", cf. Greek ἔφερε, Sanskrit abharat), and like Greek Phrygian seems to have maintained word-initial laryngeals before a consonant (Phrygian onoman "name (acc)", Greek ὄνομα; but Latin nōmen, Sanskrit nāma.)

-Phrygian seems to have undergone a Grimm's Law-like shift in consonants, in which voiced plosives merged with voiceless ones and voiced aspirates lost their aspiration. There are still some unexplained exceptions to this rule, and it is unclear whether it operated under all circumstances; for example, Phrygian bekos "bread" is thought to come from a root *bʰeg-, whence also English bake, but PIE *pōds yielded podas, not potas. The jury is still out. Other, minor changes include palatalization of *k to /ts/ before /i e/ (and, probably, also of *g and *gʰ to /dz/); merger of the velar and labiovelar series when not palatalized; and loss of *w before /o/.

-Grammatically, Phrygian is within spitting distance of Greek. Nouns retain nominative, genitive, accusative, and dative cases, three genders, and a singular and a plural; the endings are very recognizably Greek-like. Verbs retain active and middle voices (the extant middle forms deriving from the so-called "r-passive" found in Italo-Celtic and Tocharian: active addaket, middle addaketor), as well as the indicative, subjunctive, optative and imperative moods. The 3s ending ended in -s in some formations; it is unclear where it comes from (possible a palatalization of *t before *i). There may also have been a future formation in -s- related to the Greek s-future.