c. 1200, aslepe, o slæpe, from Old English on slæpe (see sleep). The parallel form on sleep continued until c. 1550. Of limbs, "numb through stoppage of circulation," from late 14c. Meaning "inattentive, off guard" is from mid-14c.
1. He was already asleep in the bed, which smelled faintly of mildew.
2. He fell asleep just past midnight with tolerable ease.
3. Sister Francesca entered the chapel, took her seat, and promptly fell asleep.
4. His eyes were shut and he seemed to have fallen asleep.
5. Sam snuggled down in his pillow and fell asleep.