The Sidetic language is a member of the extinct Anatolian

Anatolian languages

The Anatolian languages comprise a group of extinct Indo-European languages that were spoken in Asia Minor, the best attested of them being the Hittite language.-Origins:...

 branch of the Indo-European language family known from legends of coins dating to the period of approx. the 5th to 3rd centuries BC found in Side

Side

Side was an ancient Greek city in Anatolia, in the region of Pamphylia, in what is now Antalya province, on the southern Mediterranean coast of Turkey...

 at the Pamphylia

Pamphylia

In ancient geography, Pamphylia was the region in the south of Asia Minor, between Lycia and Cilicia, extending from the Mediterranean to Mount Taurus . It was bounded on the north by Pisidia and was therefore a country of small extent, having a coast-line of only about 75 miles with a breadth of...

n coast. The Greek historian Arrian

Arrian

Lucius Flavius Arrianus 'Xenophon , known in English as Arrian , and Arrian of Nicomedia, was a Roman historian, public servant, a military commander and a philosopher of the 2nd-century Roman period...

 mentions the existence of a peculiar indigenous language in the city of Side.
Sidetic was probably closely related to Lydian

Lydian language

Lydian was an Indo-European language spoken in the region of Lydia in western Anatolia . It belongs to the Anatolian group of the Indo-European language family....

, Carian

Carian language

The Carian language is an extinct language of the Luwian subgroup of the Anatolian branch of the Indo-European language family. The Carian language was spoken in Caria, a region of western Anatolia between the ancient regions of Lycia and Lydia, by the Carians, a name possibly first mentioned in...

 and Lycian

Lycian language

Lycian language refers to the inscriptional language of ancient Lycia, populated by Lycians, as well as its presumed spoken counterpart.-The speakers:...

.