I am not a linguistics expert, and I cannot confirm when the letter J came into common use in the Latin alphabet that we use.  First of all, the Hebrew, Aramaic and Greek alphabets were not the same ones we use.  Their letters do not correspond exactly to letters in our Roman alphabet with English pronunciations of those letters.   Besides, it is not possible to know exactly how a particular letter was pronounced two thousand years ago.  There are two issues, in principle, which is the written letter used and the pronunciation of that letter. Therefore, I conclude that this is a non-issue and, in my opinion, people waste their time and energy worrying about the difference between a y and a j in a name–as if God would care about this!!!!

Nevertheless, if I understand correctly, the Aramaic/Hebrew name Jesus was probably closer to Yeshua than to Joshua or Jesus.  The English name Jesus is closer to the Greek version of the name that it is to the Aramaic version of the name. Jesus is a transliteration of   Ιησούς   Consider my own name. John.  In some languages John is Juan, Jean, Johannes, Yohan, Iovan, Joao (Portuguese), Dzhon (Russian), Jan (Polish) and many more.  They are all the same name.  Which is the right one?  All are the right one, and a debate over this is a waste of breath.

So, whatever you read may or may not be completely accurate, and debates over the use of a J or a Y in the name of Jesus are probably not a good use of our time and energy.  However, it is probably true that the name by which Jesus was addressed during his life was probably closer to Yeshua than it was to Jesus.

Some Christian groups try to distinguish themselves as more legitimate because they use a more proper pronunciation of the name of Jesus (or of God).  These people, to use the expression, are barking up the wrong tree.  If we want to be more Christian then we ought to behave more like Jesus and Jesus did not spend a moment worrying about how to pronounce words properly, as far as we know.

John Oakes