If there were only three original languages; Hebrew, Latin, and Greek, where does the name Jesus come from? None of these languages had a J in their alphabet.

Jesus" is an Anglicized form of the Greek name Yesous found in the New Testament. Yesous represents the Hebrew Bible name Yeshua, which occurs as "Jeshua" in English Bibles (Ezra 2:2; Neh 7:7).

In Medieval English the "J" was pronounced as a "Y." "Yehoshua"Yeshua, in turn, is a shortened form of the name Yehoshua ("Joshua" in English Bibles).

Moses' right-hand man, Joshua, has three names in the Bible. Originally, it was Hoshea, but Moses changed it to Yehoshua (Num 13:16). During the Babylonian Exile, it was shorted to Yeshua (Neh 8:17

Taken from - Hebrewstreams.org 

(Je′sus) [Lat. Form of the Gr. I‧e‧sous′, which corresponds to the Heb. Ye‧shu′aʽ or Yehoh‧shu′aʽ

Ancient Latin alphabet

The earliest known inscriptions in the Latin alphabet date from the 6th century BC. It was adapted from the Etruscan alphabet during the 7th century BC. The letters Y and Z were taken from the Greek alphabet to write Greek loan words. Other letters were added from time to time as the Latin alphabet was adapted for other languages.

Q "If there were only three original languages; Hebrew, Latin, and Greek, where does the name Jesus come from? None of these languages had a J in their alphabet."

As was done to the "Father" whose name Yhwh was corrupted to Jehovah so was done to the "Son" whose name Yeshoo3ah [the 3 indicates that the 'a' vowel is a guttural sound]  has been corrupted to Jesus.

Just like the "Son" cannot be blamed for not turning his head if called upon by the corrupted name that he was never called by at any point in his time on earth and which bears no resemblance to the name he was given, similarly the "Father" might not respond to those who cannot be bothered to call him by the name they see in their scriptures.

While on the topic of the real name of the "Son" it is intriguing to note that in
OT prophecies that are said to apply to "Jesus", in Isaiah  for example, he is not
mentioned by name, neither is he referred to by his title Messiah or Anointed,
However, in Psalm 20:6 we read of God saving His Messiah. The verse says, “Now know I that the LORD saveth his anointed; he will hear him from his holy heaven
with the saving strength of his right hand.”

The root of the word Yeshoo3ah has to do with the verb save. The elongated oo vowel in the middle suggests a passive form. Thus Yeshoo3ah means one who was saved. It does not mean one who saved which is Yashaa3ah. So Yeshoo3ah means saved not saviour, This makes it consistent with the prophecy in Psalm 20:6 as quoted above.