It is a centum language known mainly from place-names and the names of persons. Only fragmentary inscriptions survive, the longest being three words. There are indications that Illyrian had affinities with the more northern (Germanic and Balto-Slav) Indo-European languages rather than with its immediate neighbours. Illyrian speakers were replaced by Slavonic speakers in the Roman province of Illyricum around the seventh century CE.

There are nearly 300 inscriptions in Messapic. Many place names are shared between the two regions. The language was spoken by the Messapii, Iapyges and the Calabri who crossed over from Illyricum about 1000 BCE. Place-names of this region ending in "au" can be of Messapic origin.