What does son of the fallen one mean from hellboy?

The phrase "Son of the Fallen One" is a reference to Hellboy's lineage. In the lore of the Hellboy comics and movies, Hellboy is the son of the demon Azzael, also known as the Fallen One. Azzael is a powerful and malevolent demon who was cast out of Heaven and now resides in Hell. Hellboy's mother was a human woman who was chosen by Azzael to be the vessel for his offspring. Hellboy inherited many of his father's demonic traits, including his red skin, horns, and tail, but he was raised by humans and chose to fight for good rather than evil.