Just to clarify, the Boston Celtics are named for the Celts and vice-versa. Its all about Boston and their overwhelming pride in their Irish roots. Ireland, in turn, is quite proud of its Celtic roots and so forth.
Celtic is to Celt as Spanish is to Spain. (For those who were unclear on that point.) Yes the phonetic pronunciation is Kelt, and if Bostonians were straight on their Gaelic, they be pronouncing Celtics as Keltics. Chalk up another language blunder on the part of us silly Americans.
Wikipedia Article on Celts (a very thorough one) http://en.wikipedia.org/wiki/Celts Map of Main concentration of the Celtic peoples: http://en.wikipedia.org/wiki/Image:-..._in_Europe.png
The Celts were very widespread. I don't have a source to link to you, but I took a class in Celtic History at a university and learned a good deal there. One of those items was the fact that ruins and artifacts distinct to the Celts have been found all over modern Europe as well as parts of Turkey and North Africa. They were equal to or superior to anyone of that time period in ship making and in Metalworking they were well ahead of anyone in the world.
The Troy site found by Schlieman does appear to have seen a significant war and the ruins that are believed to be Troy (in Turkey) did see a major destruction that involved a layer of ash that dates closely to the time the Iliad would have happened in. There were also walls, but the walls of that period for Troy are ... disappointingly small and insignificant when compared to the story Homer tells us.
So there are two options: Either we are seeing the results of several generations of exaggerating the account (this is the more accepted theory currently), or you have to look for Troy and the Trojan War elsewhere.
If you decide to look elsewhere, then the theory that places Troy in the British Isles fits very well. Additionally, we know that there was significant Celtic presence in ancient Greece, ancient Turkey and many other places. Many Celts were enthusiastic seagoing peoples, so it wouldn't be surprising to see a group of them move from modern day France and England to modern day Greece and Turkey. (They landed in North America somewhere around 300BC, so why not Turkey and Greece?) The Celts were surprisingly good at preserving their histories orally. If Homer was one of those that had the memorized history passed on to him then it would explain a lot.