From the Wikipedia article in the original post:
The English form of the name "Jesus" is derived from the Latin Iēsus, which in turn comes from the Greek Ἰησοῦς (Iēsoûs). The Greek is a Hellenized form of the Hebrew name Yēšua (ישוע), which is in turn a shortened form of Hebrew Yehōšua (יהושע) or "Joshua" in English.
"Iesous" is not a Greek translation of the Hebrew "Yehosua", because it isn't a Greek word that means the same thing as the Hebrew word. It is, rather, a transliteration, an adaptation of the word itself to the Greek alphabet and Greek word-building conventions. (An example of translation would be Christos, from which we take the word "Christ." It means the same thing in Greek as Messiah means in Hebrew, despite being very different actual words.)
It's not uncommon for words to be slightly mangled in transliteration, especially between languages with different alphabets. For example, have you ever been to a Chinese restaurant and seen Peking duck on the menu? If you look at a map of China today, you won't find a place called "Peking" anywhere, because in the 1950s China came up with a new system of transliterating Chinese names to the Latin alphabet to more closely match the way the names are supposed to sound, and these days the city that used to be known as Peking in English is now written as "Beijing."