It took our human race a few years to get to the point that sounds became symbols, our alphabet. The human voice [sound] represented by something that could be visualized [ a symbol]. Then taking that symbol and turning it back into voice. Who would have thought you could do such a thing?
The Canaanites seemed to have started things off, followed by the Phoenicians, then followed by the early Greeks. A sound expressed...to a symbol written...it had to start sometime. These early writings started with the hard sounds like k, b, p, and t, and it was not until the Greeks came up with the idea of softer sounds [vowels], that things really began to take off. Etruscan, Roman, and Italic alphabet became the foundation. Each generation building upon the past.
The Celtic tongue was spoken. It was taboo to write it down, for the bards and poets had spent their life memorizing the stories and history. They would be out of work if anyone started to write something down! It was the Irish who started first to write their language and keep their history and laws. The impact of the church [Latin] was the main force in this change, but the Celtic tongue was phonetically different. As the Roman world became the Christian world, Latin became the dominate expression in all things except the local tongues (vernacular). As discussed in another post, the Anglo-Saxons (Germanic) had a word for those Celtic tribes who started speaking the Latin. They were called "Walas"!
The Welsh language had this backdrop. Only to be spoken, the poets and bards continued their positions. Consonants dominated. There was even the combination of letters ch, dd, ff, ll, ph, rh, and th which were counted as a single consonant. Vowels softened things down a bit and had both long and short sounds...a, e, i, o, u, w, and y. Other letter combinations like ng and si had their own sounds. Twenty eight letters make up the Welsh alphabet. The English consonants j, k, q, v, x, and z are omitted.
It took the Welsh several centuries before they developed their own alphabet and writing. [Following the Celtic tradition.] Of course the poets had the upper hand, having both the oral traditions and the stories intact. Their poetry is thought to be the earliest written items. [called Y Cynfeirdd] The native Welsh tales (prose) came to be called " The Mabinogion".
It is these Welsh sounds to English symbols that caused all kinds of trouble yet to come.