A lot vs. Alot: 9 Grammatical Pitfalls
1680s, "afflicted by nightmares," from hag (n.) + ridden. An old term for sleep paralysis, the sensation of being held immobile in bed, often by a heavy weight, and accompanied by a sense of alien presence. A holed stone hung over the bed was said to prevent it. Hag-ride as a verb is attested from 1660s.