Why does Celtic languages ( especially Scotish Gaelic ) lack words like W and use Bh & Mh ?
What is the logic behind attributing W sound to Bh and Mh ?
Letters like W are not used in Gaelic because a W does not accurately represent the sound that is being said in Gaelic. The language is from an oral tradition not a written one. People were speaking it not writing it originally. It was only later on that attempts were made to find a way of writing it in the alphabet that is used by English speakers. So the bh and mh sounds actually aren’t a w sound... although they might sometimes sound like it. To me they actually most often sound like a v.
I’m more of a historian than a linguist so hopefully someone can come along and give you a much better explanation- but I thought a non-technical explanation might not be a bad start for those of us like my self who get a bit lost with the linguistic and grammatical terms.
W really only accurately represents mh and bh some of the time in Irish, and never really in a Scottish Gaelic. In addition, the letter w as we know it is fairly new compared to the rest of the Latin alphabet, only dating back to about the 14th century. Old Irish had b and m lenition way before then.
One reason they still use mh and bh is to make it easier to connect the unmutated and mutated forms of words. For example, in Irish “woman” is “bean” and “the woman” is “an bhean”. Just by looking at the words I know that even though the pronunciations are different, they are different forms of the same word. The reason mh and bh are used to represent these particular sounds is because only b and m mutate to these sounds. Their lenitions overlap because they are both voiced lip consonants (meaning they are pronounced with the lips while vibrating the vocal chords).
Another reason is that once upon a time they were just ‘b’ and ‘m’. Over time their sound has changed and that change has taken on grammatical meanings as well. Keeping the original letter helps with looking things up in the dictionary.
They also aren’t pronounced the same in all positions. Inside a word they often have a ‘w’ quality (leabhar, òbh) and in some Irish dialects they’re ’w’ when broad and ’v’ when slender. Writing them with ‘v’ and ‘w’ would mean different spellings for different dialects. It would also obscure the origins of the words.
Welsh takes the other approach, changing ‘b’ and ‘m’ to ‘f’ (pronounced v). Much more straightforward for reading, but less for looking up words or understanding their components.
Yes. Whilst other comments on this page are interesting in relation to the modern situation, and may help you with the language, they do not actually answer the question. The answer, as you say, is entirely historical. The Latin alphabet, at the time that monks first arrived in Ireland (where our spelling system developed) was essentially the Classical Latin Alphabet,
A B C D E F G H I K L M N O P Q R S T V X Y Z
before variants were created (identifiable because they both look similar, and are adjacent in the alphabet)
i > j
u > v, w
Of these, k was considered an unnecessary duplicate of c, and z (which was only used in Greek words at this time) did not represent a sound found in Irish. I'm not sure if there was a qu sound in Irish at the time, but there certainly wasn't in the words that had cognates in Latin
quatuor - ceithir
quinque - còig
quando - cuine
so they managed with c. So that is basically what we had in Irish, and still have in Gaelic.
There were some other sounds, but these were mostly the result of lenition. As pointed out above, it was much easier to write the original letter, with a mark showing it had changed than to just write the new sound (as they do in Welsh - very confusing). The method was not standardized at first. A dot was popular (ċ) as was an h (ch), which they seem to have borrowed from the way they wrote Greek words (with ch, th and ph all being used in Latin for Greek sounds, which would, at the time, have been almost identical in Irish, even if they aren't all now).
So that is basically what we have today. D