Odds and Ends
Nothing is Perfect
19 12, 11:53pm
J and U arose because in classical Latin, I and V pulled double-duty. Depending on context, they could be pronounced like English 'ee' and 'oo' respectively, or like English 'y' and 'w' respectively - in other words, either as vowels or as consonants. This worked fine in Latin at the time because speakers knew from the context which pronunciation was correct, but eventually, and especially when the alphabet was adapted for other languages, people decided it would be useful to distinguish them, so they changed the letters a little to create new forms.
W is a funny one. It was brought in to represent the sound it continues to represent today in English (after some experimentation with other forms; try look up the letter wynn). Thing is, in classical Latin, that sound was already represented - as noted above, it was one of the sounds V could stand for. But by this time, most if not all of the Latinate languages in western Europe (French, Italian, Spanish etc.) had evolved to the point where they'd started pronouncing V as we do today in English, so most people had come to associate with that sound. So a new letter was needed, hence W. One interesting aside is that when people started writing Old Norse with the Latin alphabet, they actually used V the way classical Latin did. They had the English V sound too, but they could just use F for that, since just like Latin I and V, whether Old Norse F sounded like English F or V was obvious from context.