Who Were the Celts?
It's hard to say anything conclusive about the Celts, because they didn't record their history themselves. They couldn't write (with one minor exception, which we discuss later). Most everything we know about them today comes from either the archaeological evidence or the accounts of Roman visitors that were transcribed by medieval Christians.
This means that all of our written records on the Celts were filtered through two sets of biases: the Romans, who looked on them as an alien culture that needed to be conquered, and the Christians, who thought the Celts were pagans who hadn't seen the truth of Christ. And modern observers have all kinds of opinions that color their views.
The word Celt is properly pronounced kelt, with a hard initial consonant. The name of the former world-champion basketball team in Boston, however, is pronounced seltiks. If you encounter Celtics fans, don't try to correct their pronunciation.
Geographic Origins
According to classical writers, most of the people who lived in northwestern and central Europe were Celts — keltoi in Greek. Ancient writers knew of Celtic people in Spain, France, Germany, Switzerland, and modern Austria. Celts were hard to miss, because they were violent; various Celtic peoples started attacking Greek and Roman settlements around 400 B.C.E. and kept attacking as long as there was loot to be had.
The ancients thought the Celts had originated in Switzerland and spread out from there. They envisioned the Celts as a warrior people who marched from country to country, attacking civilized people and settling wherever they conquered.
Modern scholars think it more likely that the Celtic language and culture spread from group to group through trade, though there was certainly some fighting involved, too. This Celtic culture moved over the Continent and into the British Isles until, by the fourth century B.C.E., most of the people in northwestern Europe and Britain were members of this cultural group.
The biblical Galatians were a Celtic people who wound up settling in Asia Minor (modern-day Turkey) sometime in the third century B.C.E. Like the Celts in Ireland, they weren't literate, so we don't know much about their history. By the time St. Paul wrote them letters in the first century C.E., they'd begun reading and writing Greek.
Cultural Spread Is Not Conquest
Historians have long imagined ancient history as a series of peoples taking over land from one another. When they envisioned the Celts, they saw warriors who came marauding over the countryside, laying waste and taking over local wealth. While there is some truth to this picture, it seems that cultural spread was actually a much gentler process most of the time.
The people who became known as the Irish were probably a mix of indigenous peoples — remember the folks who built those mounds and tombs? — and immigrants who brought new language and technology with them. The newcomers entered Irish society by marrying the natives, although there was probably some violence as well.
Irish legend gives the impression that a bunch of warriors arrived several centuries before Christ and established chiefdoms for themselves all over the country. The Celtic languages became predominant either through military domination or because they were more prestigious for other reasons. However it happened, by the time the Romans arrived, the Irish people were speaking Celtic languages.
