Who added the word Arab? "Why Can't We [Arabs] See Things as the Rest of the World Sees Them?"
When did Egyptians become Arabs?
When they were invaded by Arabs militarily and culturally in the 7th century. Arabic is the national language, and Islam is the prevalent religion (96%).
Many Muslim Egyptians consider themselves Arabs (and usually have some small descent from the Arab conquerors), Christian Egyptians don't, and some Muslim Egyptians don't. Secular Egyptian nationalism after the manner of Nassar considered itself part of Arab nationalism.