The "ghoul" comes from Arabic folklore; these remain a part of present-day superstition, perhaps in part because they are explicitly acknowledged in Islam (see Al-Rawhi, Ahmed, The Mythic Ghoul in Arabic Culture [Cultural Analysis 8 (2009): 45-69]).
Shakespeare refers to corporeal walking dead, raised by enchantment, in The Tempest (1611): "graves at my command / Have waked their sleepers, oped, and let 'em forth / By my so potent art" (act 5, scene 1).
H. P. Lovecraft's Herbert West: Reanimator (1921) was an early Frankenstein-inspired horror story about insanely violent resurrected undead (the trailer for the very enjoyable 1985 film is on YouTube, here). The African/Haitian zombi--the slave resurrected by voodoo, from which the name originates--first appears in modern Western fiction in Richard Seabrook, The Magic Island (1929). Soon after (1932) came the first major zombie film, "White Zombie," starring Bela Lugosi--the famous Dracula of the '30s--which may be seen in its entirety on YouTube, here.
Zombies became prominent characters in comic books--as early as the 1940's, Donald Duck was menaced by Bombie the Zombie--but in time they became the center of the comics-censorship fight of the 1950's. Frederic Wertham's book Seduction of the Innocent demonized comics for their bad effect on young readers, and he along with Estes Kefauver prompted the Senate Subcommittee on Juvenile Delinquency to hold hearings in 1954. William Gaines, the editor of the EC horror comics (memorialized by Stephen King and George Romero in the 1982 film Creepshow), blew his testimony--in part due to prescription medicine--and the Comics Code Authority was created. Their first priority was to ban depiction of "the walking dead" (which tells you where Kirkman got the title for his own comic series). The Code was not finally dropped till 2011... by that time, Archie Comics was the only member left. (Too bad they never did an Archie zombie comic.... if Archie was a zombie, he couldn't decide whether to eat Veronica or Betty... and of course, zombie Jughead would just eat everybody.) The zombie ban in comics helps to underscore how disturbing this material was considered to be. As late as 1980, a "Living Dead" parody sketch on the ABC show Fridays (Diner of the Living Dead) caused so much consternation that the cast had to do an on-air apology for the broadcast.
The advent of cable TV and home video may have done something to help zombies get more mainstream from the '80s onward.
The readings linked below examine the Germanic draugr and vampire, which is perhaps the most foundational to the concept of our modern zombie. This ancestry also dovetails rather closely with the origin of the modern zombie film in Romero's Night of the Living Dead, which itself is riffing off Richard Matheson's I Am Legend, as well as the original film version, The Last Man on Earth. This book does not invent the "Last Man" genre. Arguably, this kind of story--focusing on a man alone, with lengthy descriptions of how he single-handedly replaces or substitutes for modern technology to support his lifestyle--gets its biggest start in Western literature with Defoe's Robinson Crusoe... if you read Matheson carefully, you'll spot a nod to Defoe along the way. Another author who admits being inspired by Robinson Crusoe is Dr. Theodore Kaczynski, better known as the Unabomber. His theories about the inevitable collapse of modern technological-industrial civilization have gained some traction since they were first publicized, and give us one alternate perspective for evaluating the modern fear of cultural collapse. Mary Shelley, the author of Frankenstein, is credited for creating the theme of the modern-day last survivor in her work, The Last Man (1826), although the piece enjoyed little success when first published. Post-WW II science fiction includes many examples, some described on this blog.