I found the following here


A Rose by Any Other Name ...

The part that the Celts played in shaping European civilization has slowly evolved during the past few decades, from a time when the Celtic people were not even mentioned in school textbooks on European history. That role provokes increasing wonder but little controversy. Such is not the case on one feature of the Celts, however. There has arisen an increasingly fractious dispute over how to pronounce the name of the people: is it "selt-Celt" or "kelt-Celt"? It is important to understand that no one is around who heard the word pronounced by the people who called themselves Celts, some two thousand or so years ago. In the virtual absence of a written record left by the Celts themselves, etymologists have to rely on clues left in languages for which we have some knowledge of how words and letters were pronounced. Present-day authorities are divided; for example, Webster's Seventh New Collegiate Dictionary prefers "selt-Celt," while the American Heritage Dictionary prefers "kelt-Celt".

For the word "Celt", there are two solid clues, mutually contradictory. The Greeks transliterated the word into "keltoi" (here I use Roman letters instead of Greek, for clarity). That might lead us to the conclusion that the Celts called themselves "Kelts." But the Greeks used the letter "k" to transliterate both the sibilant "s" sound and the plosive "k" sound, so the word "keltoi" is not conclusive.

In Latin, the word is written "celtoi" or "celtai." If that word was derived directly from the Celtic people's pronunciation, it would indicate that the correct pronunciation is "selt-Celt". But there is some indication that it was derived from the Greek word "keltoi," leaving us with little to go on, as it was common to convert Greek "k" sounds (plosive) into Latin "c" sounds (sibilant). Hence, the Greek "kentrum" became Latin "centrum," from which we get the English word "center". This is a common development; the Latin "caesar" was converted in German into "kaiser" (plosive), but into "czar" in Russian, retaining the Latin sibilant sound.

Unfortunately, primitive Celtic language differentiated into several branches many centuries ago, and the word "Celt" in today's Gaelic (for example) is a late back-transformation from a different language, probably English. No other European language gives much help. So we are left with the contradictory clues, the Greek "keltoi" and the Latin "celtai." Which is correct - "selt-Celt" or "kelt-Celt"? There are two questions here - first, what did the people call themselves in, say, 500 BC? Second, how should the word be pronounced in modem English?

To the first question, there is no solid answer, and probably never will be. Evidence slightly favors "selt-Celt," but it is by no means conclusive. To the second question, we refer to the rules of pronunciation for our language, one of which is, "c" before "e" is always sibilant, except for a very few foreign words used in English (such as the Italian word "cello", with the sound "ch"). That is true regardless of the earliest origin of the root word - such as the Greek "kentrum" evolving into Latin "centrum" and thence into English "center." The plosive "kelt" heard with increasing frequency today may be a good guess on the original people's pronunciation, but it is bad English.

The evolution of the "kelt-Celt" pronunciation is recent. For both English and American authorities, the word was pronounced "selt-Celt" universally during the late 1800s and early 1900s; see English lexicographers John Craig (1849) and Benjamin Humphrey Smart (1836); American Noah Webster (1828). Webster's, American College, and Funk & Wagnalls dictionaries up through the 1950s universally used "selt-Celt" as the preferred or only pronunciation. The dominant American grammar authority John Opdycke in 1939 wrote " 'Celtic' may also be spelt 'Keltic', and the two forms are accordingly pronounced 'sell-tik' and 'keU-tik'..." The Oxford English Dictionary in 1928 sanctioned only "selt-Celt" and "seltic-Celtic". The giant among English usage authorities, H. W. Fowler, wrote in 1926 "The spelling C- & the pronunciation s-, are the established ones, & no useful purpose seems to be served by the substitution ofk-." In 1999 Charles Elster, the dominant American authority in orthoepy (proper pronunciation of words) held firmly with "selt-Celt," describing "kelt-Celt" as a "beastly mispronunciation."

The "kelt-Celt" heresy arose in England after the 1950s and spread throughout the rest of Britain and in the last couple of decades into the United States as well. In 1989 the Oxford English Dictionary finally recognized the "kelt-Celt" pronunciation, although still listing "selt-Celt" as preferred. It is now fashionable to hear "kelt-Celt" at Scottish Games in the United States; indeed, I am sometimes viewed as illiterate when I adhere to the orthoepically and historically correct "selt-Celt." Interestingly, the Glasgow Celtic football team (which means rugby, not American football) is still called the "selticks."

There are those who will point to the Greek origin and claim that accuracy requires us to violate the rule of English pronunciation and recast the word as "kelt-Celt". There is the attendant requirement, for consistency, to do so with all English words that derive ultimately from Greek. Thus, those who insist on "kelt-Celt" should be prepared to go to the local building supply "kenter" to buy some "kedar" lumber - as both "center" and "cedar" derive from Greek words - or change the spelling to "Kelt" to conform to English rules. Elster proposes a test: "Try going to a Boston Celtics basketball game and yelling, 'Go, Kel-tiks!' If you can get out of there without being slam-dunked, you can say it however you want." None of which can detract from the growing appreciation of a people who had an enormous influence on European history, and whose traits of fierce independence, unparalleled military prowess and courage, and love of education, science, and the arts continue to wield a powerful influence on present-day world civilization.