The Celts were a group of peoples that occupied lands stretching from the British Isles to Gallatia. The Celts had many dealings with other cultures that bordered the lands occupied by these peoples, and even though there is no written record of the Celts stemming from their own documents, we can piece together a fair picture of them from archeological evidence as well as historical accounts from other cultures.
The first historical recorded encounter of a people displaying the cultural traits associated with the Celts comes from northern Italy around 400 BC, when a previously unkown group of barbarians came down from the Alps and displaced the Etruscans from the fertile Po valley, a displacment that helped to push the Etruscans from history's limelight. The next encounter with the Celts came with the still young Roman Empire, directly to the south of the Po. The Romans in fact had sent three envoys to the beseiged Etruscans to study this new force. We know from Livy's The Early History of Rome that this first encounter with Rome was quite civilized:
[The Celts told the Roman envoys that] this was indeed the first time they had heard of them, but they assumed the Romans must be a courageous people because it was to them that the [Etruscans] had turned to in their hour of need. And since the Romans had tried to help with an embassy and not with arms, they themselves would not reject the offer of peace, provided the [Etruscans] ceded part of their seperfluous agricultural land; that was what they, the Celts, wanted.... If it were not given, they would launch an attack before the Romans' eyes, so that the Romans could report back how superior the Gauls were in battle to all others....The Romans then asked whether it was right to demand land from its owners on pain of war, indeed what were the Celts going in Etruria in the first place? The latter defiantly retorted that their right lay in their arms: To the brave belong all things.
The Roman envoys then preceded to break their good faith and helped the Etruscans in their fight; in fact, one of the envoys, Quintas Fabius killed one of the Celtic tribal leaders. The Celts then sent their own envoys to Rome in protest and demand the Romans hand over all members of the Fabian family, to which all three of the original Roman envoys belonged, be given over to the Celts, a move completely in line with current Roman protocol. This of course presented problems for the Roman senate, since the Fabian family was quite powerful in Rome. Indeed, Livy says that:
The party structure would allow no resolution to be made against such noblemanm as justice would have required. The Senate...therefore passed examination of the Celts' request to the popular assembly, in which power and influence naturally counted for more. So it happened that those who ought to have been punished were instead appointed for the coming year military tribunes with consular powers (the highest that could be granted).
The Celts saw this as a mortal insult and a host marched south to Rome. The Celts tore through the countryside and several battalions of Roman soilders to lay seige to the Capitol of the Roman Empire. Seven months of seige led to negotiations wherby the Celts promised to leave their seige for a tribute of one thousand pounds of gold, which the historian Pliny tells was very difficult for the entire city to muster. When the gold was being weighed, the Romans claimed the Celts were cheating with faulty weights. It was then that the Celts' leader, Brennus, threw his sword into the balance and and uttered the words vae victis "woe to the Defeated". Rome never withstood another more humiliating defeat and the Celts made an initial step of magnificent proportions into history.
Other Roman historians tell us more of the Celts. Diodorus notes that:
Their aspect is terrifying...They are very tall in stature, with ripling muscles under clear white skin. Their hair is blond, but not naturally so: they bleach it, to this day, artificially, washing it in lime and combing it back from their foreheaads. They look like wood-demons, their hair thick and shaggy like a horse's mane. Some of them are cleanshaven, but others - especially those of high rank, shave their cheeks but leave a moustache that covers the whole mouth and, when they eat and drink, acts like a sieve, trapping particles of food...The way they dress is astonishing: they wear brightly coloured and embroidered shirts, with trousers called bracae and cloaks fastened at the shoulder with a brooch, heavy in winter, light in summer. These cloaks are striped or checkered in design, with the seperate checks close together and in various colours.
[The Celts] wear bronze helmets with figures picked out on them, even horns, which made them look even taller than they already are...while others cover themselves with breast-armour made out of chains. But most content themselves with the weapons nature gave them: they go naked into battle...Weird, discordant horns were sounded, [they shouted in chorus with their] deep and harsh voices, they beat their swords rythmically against their shields.
Diodorus also describes how the Celts cut off their enemies' heads and nailed them over the doors of their huts, as Diodorus states:
In exactly the same way as hunters do with their skulls of the animals they have slain...they preserved the heads of their most high-ranking victims in cedar oil, keeping them carefully in wooden boxes.
Diodorus Siculus, History.
The people who made up the various tribes of concern were called Galli by the Romans and Galatai or Keltoi by the Greeks, terms meaning barbarian. It is from the greek Keltoi that Celt is derived. Since no soft c exists in greek, Celt and Celtic and all permutations should be pronounced with a hard k sound.
It is interesting to note that when the British Empire was distinguishing itself as better and seperate from the rest of humanity, it was decided that British Latin should have different pronunciation from other spoken Latin. Therefore, one of these distinguishing pronunciational differences was to make many of the previously hard k sounds move to a soft s sound, hence the Glasgow and Boston Celtics. It is the view of many today that this soft c pronunciation should be reserved for sports teams since there is obviously nothing to link them with the original noble savegery and furor associated with the Celts.
There was a unifying language spoken by the Celts, called not suprisingly, old Celtic. Philogists have shown the descendence of Celtic from the original Ur-language and from the Indo-European language tradition. In fact, the form of old Celtic was the closest cousin to Italic, the precursor of Latin.
The original wave of Celtic immigrants to the British Isles are called the q-Celts and spoke Goidelic. It is not known exactly when this immigration occurred but it may be placed somtime in the window of 2000 to 1200 BC. The label q-Celtic stems from the differences between this early Celtic tounge and Italic. Some of the differences between Italic and Celtic included that lack of a p in Celtic and an a in place of an the Italic o.
At a later date, a second wave of immigrants took to the British Isles, a wave of Celts referred to as the p-Celts speaking Brythonic. Goidelic led to the formation of the three Gaelic languages spoken in Ireland, Man and later Scotland. Brythonic gave rise to two British Isles languages, Welsh and Cornish, as well as surviving on the Continent in the form of Breton, spoken in Brittany.
The label q-Celtic stems from the differences between this early Celtic tounge and the latter formed p-Celtic. The differences between the two Celtic branches are simple in theoretical form. Take for example the word ekvos in Indo-European, meaning horse. In q-Celtic this was rendered as equos while in p-Celtic it became epos, the q sound being replaced with a p sound. Another example is the Latin qui who. In q-Celtic this rendered as cia while in p-Celtic it rendered as pwy. It should also be noted that there are still words common to the two Celtic subgroups.
As an aside, take note that when the Irish expansion into Pictish Britain occurred (see below), several colonies were established in present day Wales. The local inhabitants called the Irish arrivals gwyddel savages from which comes geídil and goidel and thus the Goidelic tounge.
Ireland used to be divided up into five parts, the five fifths. There was a northern fifth, Ulster, a western fifth, Connaught, a southern fifth, Munster, an eastern fifth, Leinster and a middle fifth, Mide.
The Ulster Cycle is a set of stories which are grounded in the five fifths. Indeed, they are primarily concerned with Cú Chulainn, the Ulster hero and his king, Conor Mac Nessa in their wars against the king and queen of Connaught, Ailill and Maeve. These figures play a prominent role in the what may be the greatest story of the Ulster Cycle, the Táin Bó Cúailnge, The Cattle Raid of Cooley.
Sometime after 300 AD, Ulster became steadily less important in status among the five farthings and the ruling family of Mide, the Uí Néill Sons of Niall started to take over large parts of Connaught and most of Ulster. A similar move was made in Muster by the ruling family of Munster, the Eoganachta family. Thus was Ireland divided almost entirely into two halves.
The people of Ulster were pushed to a small coastal strip bordering the Irish Sea. The kingdom changed it's name to Dál Riata. Yet eventually Dál Riata fell under the rule and influence of the Uí Néill. This family, not content with the boundry presented by the sea, launched colonies across the Irish Sea into then Pictish Britain. Thus was Scotland founded, for it was these Uí Néill that the Romans called Scotti, not the original Picts.
Indeed, it was this Irish Expansion which led to Christianity in Scotland in 563 AD. St. Columba, the patron saint of Scotland, was a member of a powerful family in Dál Riata and in order to keep his ties in Ireland he settled on an island that was close to both Scotland and Ireland, Iona. Of course, even more bizarre is the fact that St. Patrick, the man responsible for bringing Christianity to Ireland in the first place, was from Wales.