Anyone looking up the origin of the word rest will find two dictionary entries, not one. English uses the same spelling for a pause from work, a support under a chin, a silence in a bar of music, and the leftover slice of the pie. The last of those is not a late sense of the first. It arrived from French while the sleep-and-pause word was already centuries old on English soil.
What English uses it for
In ordinary speech, rest is first of all relief after effort: sleep, a break, quiet of mind. It is also stillness, as when a rolling stone comes to rest, and a polite name for death. It names objects that hold something up — an armrest, a cue rest — and, in music, both a measured silence and the sign that marks it.
Beside all that sits the rest of the day, the rest of us: remainder, the others. Native speakers treat that as the same word. Historically it is not.
Inherited from Germanic
The repose noun is inherited. Old English already used ræst and reste for rest, for a bed or couch, for a pause from labor, and for mental quiet. The matching verb was ræstan or restan: to lie down, to stop moving or working, to lie in the grave, to stand as on a support. Both passed through Middle English as rest and resten without a break in the line.
Behind Old English stands Proto-West Germanic rastu and Proto-Germanic rastō. Cognates are easy to point to: West Frisian rêst, German Rast, Swedish rast. Dutch rust is the everyday sibling. Gothic rasta meant a mile or a stage of a journey. Old Norse röst, also recorded as rost, named a league, the stretch after which a traveler stops. Old High German rasta could mean both rest and a league of miles. Old Saxon resta could name a resting place and a burial place.
That overlap is the best clue we have to the prehistoric sense, and it is also where handbooks disagree. Some take the original Germanic meaning to be a measure of distance, a word from travel by stages, with repose as the halt between stages. Others reverse the story: repose first, then the interval between resting places. Learner dictionaries from Oxford present the league-or-mile root as the Germanic starting point. Other etymological surveys simply call the deeper source uncertain. Either reading can be true; the comparative evidence does not force a single order.
A root that will not sit still
Past Germanic, the reconstruction is disputed. The Leiden handbook by Guus Kroonen links rastō to the same root as a verb for rushing and a noun for a course or run, from a proposed Indo-European form meaning to flow or rush, plus a suffix that would yield an interval. A rival comparison goes to a root that would mean to rest. That second idea looks neater on the page; Kroonen does not prefer it. Distant look-alikes sometimes listed — Greek erōē for respite, Sanskrit ramate for staying still — belong to that uncertain zone. The honest summary is inherited Germanic, further ancestry not settled.
The verb is the same family. Proto-Germanic rastejanan gives Old Saxon restian, Dutch rusten, German rasten, Danish raste. By the early thirteenth century English could rest something on a support. By the late fourteenth the verb also meant to cease from an activity and to rely on something. American legal English later added the defense rests, ending a side's presentation of evidence, first recorded around 1905. Rest up, recover strength, is American from the 1890s.
How the native senses fanned out
Old English had already bundled several ideas: stopping work, a place to lie, peace of mind. Middle English kept them and made death a kind of rest: the phrase at rest for dead is attested from the mid-fourteenth century, on the image of a last sleep. A rest as a thing something leans on appears in the 1580s and later yields the furniture compounds and the snooker rest. Music took the word in the 1570s for an interval of silence and for the notational mark.
Later English kept adding local uses without borrowing. Highway rest stops are recorded around 1970. American colloquial give it a rest, meaning stop talking about that, is from the 1920s. Physics still uses rest for the absence of motion. None of these need a foreign source; they are the inherited word stretching into new rooms of the language.
Remainder: a Latin word in French clothes
The rest meaning remnant enters English in the early fifteenth century from Old French reste, from rester, to remain. Latin restare is transparent: the prefix re- (back) plus stare (to stand), literally to stand back, hence to be left. The same stand-root underlies English stand, status, and statue. By the 1530s the noun could also mean the others, those not already named.
The matching English verb, from the mid-fifteenth century, meant remain, continue to exist. That sense is now rare except in rest assured and a few other fossils. Rest with, be in the power of, is nineteenth century. Because the two verbs look identical, they have bled into each other. A conclusion that rests on evidence can be read as leaning (Germanic) or remaining (Romance). Phrases such as rest you merry, the greeting behind the well-known Christmas carol line, use the remain-verb with an old adverb merry: remain well, be happy. Modern print often drops the comma after merry and so hides the grammar.
From the Latin family English also took restive. In the fifteenth century, of an animal, it meant not moving forward. By the late seventeenth century the dominant sense had flipped toward unmanageable, then toward fidgety. The pull of the unrelated Germanic rest, and of restless, helped that reversal: a word that once meant unwilling to move now names the opposite fidget.
A minor third rest, the lance support on a breastplate, is a shortening of an Old French word related to arrest, a stopping. It is a side path, not the main fork.
One fact that keeps the pair apart
If a single leftover is useful, take restive. It has nothing to do with a nap. It is the remainder-family in disguise: a creature that remains, that will not go — and then, by a twist English never planned, a creature that will not stay still.