The word Celt is Greek in origin being derived from the word Keltoi meaning 'barbarian' or 'stranger.' The German equivalent is Kelten. The Romans referred to these people as Galli from where were get the word Gaul and also the word Gaelic.
Indo-European Roots
The Celts or Gauls are/were part of Indo-European civilization. The term Indo-European refers to a broad cultural, linguistic, and racial group that was/is distributed from Europe to South Asia.
The Gaelic language falls into the Indo-European language group which includes most of the ancient and contemporary languages spoken in Europe, Russia, Central Asia and South Asia. These include languages such as Sanskrit (and many other North Indian languages), Persian, Latin (and the Romantic Languages of Europe), Greek and many other European languages.
Kurgan and Danubian Civilization
The Celtic and North Indian Civilization have some common historical roots. They both can be traced back to 3000 B.C. and the Kurgan (Russian "mound") culture [burial mounds] that existed North of the Caspian Sea. In 2400 B.C. 'Kurgans' migrated South and West and by 2000 B.C. they entered Turkey.
By 1600 B.C. they came to form the Hittites (Turkey), Mycenaeans (Greece), and the Danubians (Mouth of Danube). Descendants of the Kurgan civilization also formed the basis for "Aryan" migrations and invasions of South Asia between around 1500 B.C..
By 1200 B.C. Danubians became established in Northern Europe. Around 1000 B.C. Danubian culture was influenced by Scythian culture of the Russian steppes. This era marks the Proto-Celt period.
Archaeological Evidence
Archaeological sites at Hallstatt, in present day Austria, reveal an early Iron Age (800-500 B.C.) civilization. In 1734, a salt miner found the remains of a Celt who had died in about 300 B.C.. The body was preserved in salt. In 1846 excavations revealed 2000 Iron Age graves in this location.
At La Tene, Switzerland later Iron Age (500-50 B.C) artifacts were found. In 1853-54 the lowering of waters of lake Neuchatel revealed many Celtic artifacts. Excavations in 1880-85 and 1907-17 produce weapons, utensils and other artifacts with designs that differ from the Hallstatt site.
Other evidence of early Celtic Civilization include burial mounds, fortresses/fortifications and references in Greek and Roman writings.
Generally speaking, the Ancient Greeks and Romans referred to the peoples living in the north and West as Celts and Gauls respectively. The Celts displayed a high degree of cultural homogeneity including social organization and language. As such they have come to be recognized as a distinct people. At the same time they are related to the Greeks and Romans through common Indo-European roots.
Sources:
The Celts 1986 documentary series produced by the British Broadcasting Corporation written and presented by Frank Delaney
