late 14c., from rest (n.1) + -less. A general Germanic compound (Frisian restleas, Dutch rusteloos, German rastlos, Danish rastlös). Meaning "stirring constantly, desirous of action" is attested from late 15c. Related: Restlessly; restlessness. Old English had restleas "deprived of sleep."
the restless sea
the restless wind
a restless night
rested
restful
restitute
restitution
restive
restless
restock
restoration
restorative
restore
restrain