With all due respect, unlike other Abrahamic religions (Judaism and Christianity) and others like Hinduism, Buddhism etc. Islam does not take its name from any person, place or object. In that respect, it is unique.
The meaning of the Arabic word ‘Islam’ in the simplest term, means, ‘Peace, Submission’.
And a Muslim is someone who submits to Allah (God) willing without any compulsion.
Therefore, anyone who willingly submits to the revelation of God is a Mulsim.
Prophet Jesus (peace be upon him) is a Muslim, just like Prophets Adam, Enoch, Noah, Abraham, David, Solomon and Moses, peace be upon them all, before him. They all willingly submitted themselves to God.
It’s as simple as that.
Similarly, just want to elaborate on the meaning of the Arabic word ‘Kafir/Kuffar’ which you may or may not have heard about.
It literally means to ‘conceal/disbelieve’. In terms of Islam, it means people who know that God is One, and the religion is true but they on purpose hide the truth from themselves and others and activly choose to disbelive, hence they are called as Disbelievers in God and his Messengers. Which they are free to do as there are no compulsion in region. If anyone says otherwise, they are lying.
If I’ve made any mistakes then they are mine alone.