Two, and also a bond
Today English couple names a pair: two people in a relationship, two items taken together, or, more loosely, a small handful. As a verb it still means to join things, and in some registers to join sexually. The origin of the word couple is less a love story than a fastening story. The everyday noun is doing two jobs that Latin already combined: naming the link, and naming the things that the link holds.
From French into Middle English
English did not inherit the word from Old English. It borrowed both the noun and the verb from Old French, where twelfth-century cople (later couple) could mean lovers or a married pair. The French verb copler / coupler meant to join things together. Modern French still splits the noun by gender in a way English never copied: masculine couple for two partners, feminine couple for a neck-tie that holds animals side by side and, in some regions, for a pair of things.
Dictionaries do not agree on the exact first English year. Several place the verb around 1200, slightly before the noun; the Oxford English Dictionary’s earliest noun evidence is from about 1320, in the Middle English romance Orpheo, while other references put the noun in the late 1200s. All of that is still the Middle English period, after Norman French had been feeding vocabulary into English for generations. Anglo-French spellings such as cuple sit behind the modern form.
Middle English also used the word for a leash that held two hunting dogs, for a pair of roof timbers, and for two people joined in marriage. Those are not later poetic extras. They are the old sense of a fastener made visible in daily work.
A Latin diminutive built on together and fasten
Old French had the word from Latin cōpula, a band, tie, or leash. Latin writers used it both for a physical thong and, figuratively, for a bond of love or friendship. The noun is a contraction of an earlier coapula: the prefix con- (together), the verb apiō / apere (to fasten or join), and a diminutive ending. The same Latin verb family gives English apt, adapt, and inept: things fitted, or badly fitted. From the related verb cōpulāre English later took copulate, first in a general sense of joining, then in a sexual one.
When scholars later borrowed Latin cōpula itself into English as copula, they created a doublet. Couple is the everyday French path; copula is the classroom path, now mainly the linking verb that joins a subject to a predicate, and also a technical term in statistics. Italian kept an inherited twin, coppia, for a pair, while taking copula again as a learned word. Catalan and Occitan cobla show the same Latin source in other Romance languages. Dutch koppel and the German verb koppeln are later borrowings from this Romance cluster, not native Germanic cousins of the English word.
The deeper Indo-European reconstruction is usually given as a compound of kom- (together) and a root ap- (to take, reach, or attach). That reconstruction is a scholarly proposal, not a recorded form, and sources differ on how tightly to tie Latin apere to Greek verbs of touching.
From the tie to the pair to a few
The oldest meaning in English is not two people in love. It is two of the same kind connected or considered together, with married or romantic partners as a prominent special case, and, from the mid-fourteenth century, the connector itself: the thing that unites two. The verb tracks the same history: first to link, then, by the mid-1300s, to unite in marriage, and by about 1400 to join sexually.
Because a couple was two things held by one bond, the word could name the bond (a dog couple, a coupling) or the pair. Architecture kept couple for a pair of rafters. Mechanics later reused it for two equal forces that produce a pure turning effect; Louis Poinsot’s French textbook of 1803 made couple a technical term in statics, and English dynamics records the sense in the 1850s. Electricity added the voltaic or galvanic couple in the 1860s: two dissimilar metal plates that generate a current. Thermocouple is the same idea with heat. Verse borrowed a related diminutive, couplet, for two successive lines.
The most familiar modern stretch is quantitative. A couple of still often means two, but it also means an indefinite small number, a few. That loosening is old in informal English and is stronger in North American usage, especially when of drops out (a couple minutes, a couple hundred). Usage books still argue about the dropped of; the older construction with of remains the safer written form if a writer wants two rather than several.
A leftover from the leash
One concrete reminder of the Latin leash sits in older hunting English: dogs were said to run in couples when they were joined by a short tie. Shakespeare could still use that image for people kept together. The romantic pair on a greeting card and the thermocouple in a kiln look like different words. They are the same borrowing, still doing what cōpula did: holding two things so they count as one unit.