It is a greek word and Jesus was not a Greek person. So why you call your Jesus as christ??
The answer to your question is simply, but the real question is this.
If Jesus wasn’t greek, why did the Quran arabize the Greek name of Jesus,
Iēsous, and not the Aramic name of Jesus,
Yeshua ? I mean the Arabic speaking Christian refer to Jesus as Yashua, which is the arabization of the Aramic, Yeshua.
Isn’t that the real question??? I mean, since you believe the Quran came directly from God??? Why did
God chose, Isa, the Arabization of the Greek,
Iēsous, name for Jesus, and not Yashua, the Arabization of the Aramic,
Yeshua, which is the name Arabic speaking Christians refer to Jesus???
But to answer your question.
Jesus’ primary language was Aramic, and language of the gentiles of his area and time, was Greek and also there were many Greek speaking Jews, which is why 72 Jewish scholars two hundred years before Jesus, took the time to translated the Hebrew Old Testament into Greek which is known as the Septuagent, which is quoted frequently in the New Testament by Jesus. In the New Testament, Jesus uses quotes from the both the Greek and Hebrew Old Testament. There is a mixture.
Jesus knew and spoke Greek.