Abdul Alhazred is a fictional character created by American horror writer H. P. Lovecraft. He is the so-called "Mad Arab" credited with authoring the fictional book Kitab al-Azif (the Necronomicon), and as such is an integral part of Cthulhu Mythos lore.
Abdul Alhazred was a pseudonym adopted by Lovecraft after reading 1001 Arabian Nights in his early childhood. The name may have been invented by Lovecraft himself or the Phillips' family lawyer Albert Baker.
Abdul is a common Arabic name component (but never a name by itself). Alhazred may allude to Hazard, a reference to the book's destructive and dangerous nature, or to Lovecraft's ancestors by that name. It might also have been a play on "all-has-read", since Lovecraft was an avid reader in youth. With Abdul meaning "slave of" Abdul Alhazred could mean a slave of all that has been read, in reference to Lovecraft and his youthful all-consuming pursuit, or to his creation of the Cthulhu mythos and being a slave of it even while its creator; it more aptly applies to the character Abdul Alhazred who truly was enslaved by what he read, and became a servant of unfathomable evil.
Another possibility, raised in an essay by the Swedish fantasy writer and editor Rickard Berghorn, is that the name Alhazred was influenced by references to two historical authors whose names were Latinized as Alhazen: Alhazen ben Josef, who translated Ptolemy into Arabic; and Abu 'Ali al-Hasan ibn al-Haytham, who wrote about optics, mathematics and physics. Ibn al-Haytham is said to have pretended to be mad to escape the wrath of a ruler.
Abdul Alhazred is not a real Arabic name, and seems to contain the Arabic definite article morpheme al- twice in a row (anomalous in terms of Arabic grammar). The more proper Arabic form might be Abd-al-Hazred or Abdul Hazred. In Arabic translations, his name has appeared as Abdullah AlHa Zred : Arabic = "he fenced in", "he prohibited". Hazred could come from the Arabic word "Hazrat" meaning Great Lord with a twist that makes it sound like "red" and "hazard" both indicative of danger. It is also thought by some to be a corruption of sorts on the phrase "All has read," to imply he has read lots, and has immense amounts of knowledge. However Abdul is a common Arabic prefix meaning "Servant" and "Al" is Arabic for "the", and if "hazra" means "he prohibited", "he fenced in" or "Great Lord", then the name would mean "Servant of the Prohibited", "Servant of the Fenced in", or "Servant of the Great Lord" which would make sense considering his role, even if it is not a proper Arabic name.
Similarly, an article (written from an in-universe perspective) in the Call of Cthulhu tabletop role-playing game speculates that it may be a corruption of Abd Al-Azrad, which it claims translates to The Worshipper of the Great Devourer.
The phrase "mad Arab", sometimes with both words capitalized in Lovecraft's stories, is used so commonly before Alhazred's name that it almost constitutes a title. A reference to the "Mad Arab" in Cthulhu Mythos fiction is invariably a synonym for Abdul Alhazred. Later writers sometimes preface Alhazred with words such as "monk" (such as in the Chick parody tract "Who will be Eaten First?" by Howard Hallis) or "scholar" replacing Arab to avoid any racist overtones.