Question: Since the letter "J" was not introduced until 500 years ago, is "Jesus" the correct name for the Son of God or have we changed His name?
Answer: "Jesus" is the English word for "iesous," the transliterated Greek version of "Joshua" (English word) ... or "yehowshuwa" or "yehowshua" in the Hebrew. They both mean "Jehovah is salvation or, i.e., is the Savior." Originally, the name "Jehovah" was represented in the Hebrew manuscripts by the tetragrammaton "YHVH." Until the Masoretics put the vowel points in the Hebrew text in 500 A.D., only learned Jews could read and pronounce that.
Since God is cause of the different languages (Genesis 11:6,7), I am sure He understands them all. If English is our mother-tongue, He understands what we say to Him; and the same for any other language.
God caused some 16 different nationalities to understand Peter and the other disciples when they spoke on Pentecost; each understanding in their own known language. Read Acts 2:4-11. These were actual languages which Peter and the disciples spoke as the "spirit gave utterance" (Verse 4), and "everyone heard in their own language" (Verses 6,8,11). The Holy Spirit, who is God, on this one special occasion, gave these men the ability to speak so each could hear in their own language.
We have not "changed" God's name, we have simply translated it into another language. "Iesous," the transliterated Greek version of "Joshua," existed at the time Jesus walked the Earth in the Septuagint, which is the Old Testament translated into Greek.
By the way, the letter "J" was in existence before 500 A.D. as it is in the Latin alphabet. Just not in the ancient Greek or Hebrew alphabet.
"Neither is there salvation in any other: for there is none other name under heaven given among men, whereby we must be saved." - Acts 4:12