Isaiah uses the phrase "son of the morning" to describe someone here
Isaiah 14:12 (KJV)
12 How art thou fallen from heaven, O Lucifer, son of the morning! how art thou cut down to the ground, which didst weaken the nations!
What exactly does the phrase mean?
Isaiah chapter 14 talks of the pomp and splendour of the king of Babylon (see verse 14:4), who had ruled the nations in anger, and his fate after his overthrow by the king of Persia. He had compared himself to the morning star ('Lucifer', from Latin lucem ferre, which mean "light-bearer", a name for the dawn appearance of the planet Venus) and had thought that after his death he would ascend into heaven and sit among the stars, but was now himself persecuted. He has become weak and like one of us; he will go to hell. Second Isaiah was being ironic in calling his failed adversary the son of the morning.
