When writer Rod Temperton (who wrote the late-70s hit "Boogie Nights") was asked to work on the album, producer Quincy Jones casually suggested that Temperton should try to come up with a name himself.
Temperton's first try was Starlight. Hm.
Luckily, someone told him this was a bad idea, and in an evening of intensive brainstorming (he says he wrote down two or three hundred titles), Temperton came up with Midnight Man. It's a little easier to imagine this title working for a hit, but something came to the writer overnight. As he tells the story: "The next morning I woke up and I just said this word. Something in my head just said, 'This [Thriller] is the title'. You could visualise it at the top of the Billboard charts. You could see the merchandising for this one word, how it jumped off the page as 'Thriller'." Supernatural visitation, much?