“When I lay abed as a boy in our ranch house, listening to those trucks growl their way up highway 281, the sound of those motors came to seem as organic as the sounds of the various birds and animals who were apt to make noises in the night.”
–Larry McMurtry, Roads: Driving America’s Great Highways
Abed is the prefix a-, “in, on” (from Old English an) + bed (from Old English bedd).