Archeologists have found many referals to common names of
Yakov and
Avram in Syria (Aram) Iraq (Babel-Babelonia Assirian lands) and Iran (Persia and
Madai). So the original name
Jacob or
Yankel Yanko Janko Yago
Diego Yakoub Yanki etc. are from ancient proto-semitic languages.
Same with
Abraham,
Abe,
Avi,
Ibrahim,
Avrum, Avremi etc.
Also the name in Hebrew is with an extra glottal letter.
So it is pronounced: Ya Ackov and the A of Ackov forced through the throat. When Jews reached lands where they lost the pronunciation they remembered it by pronouncing a nasal (through the nose) letter.
Therefore Yankov, Yanko,
Yankel, Yago,
Diego.
The J for
Jacob is simply because in ancient times the y pronunciation was written with the letter J (pronounced Yay!).
Jeremiah is Yirmiya,
Judas Yehuda, Jewish is
Yehudi, and Jerusalem is Yerusholayim. BTW to this day this is the waj it is pronounced in Sweden.
PS When will the Japanese ask the rest of the world politely to call them the way they should: Yapan. (Ask any Yapanese if it's true)