A locator with several jobs
In present-day English, behind marks what sits at the rear or on the far side of a reference point. A wall can hide a garden. A runner can finish last in the field. A clock can run slow. The same form also names a cause or a backer: a person can be the force that produced a plan, or a crowd can stand in support of a candidate. In informal speech it is a polite name for the buttocks. Those later uses did not need a new coinage. They grew from the spatial one.
The word is native. It was not borrowed from French or Latin, and it was already doing adverb and preposition work in Old English.
An Old English compound
Old English had behindan, with a Northumbrian spelling bihianda among the recorded variants. Standard dictionaries place first use in the Old English period, before 1150. The form is inherited from Germanic. Middle English then passes through a crowd of spellings — bihinden, byhynde, behynde, behinde — before the modern shape settles.
The pairing itself is older than English as a separate language. Old Saxon has the matching adverb bihindan. Middle High German has behinter. The English word belongs with a West Germanic set built from the same two pieces, not with a later loan.
The prepositional use is not a Middle English upgrade. In Old English the adverb could take a dative of reference: behindan him, in the rear as regards him. Gothic used a related word, hindana, with a genitive, including a New Testament phrase that places people on the far side of the Jordan. The two constructions are cousins. Both show a directional adverb learning to take a complement.
Prefix, root, and an old “from”
The morphology is still readable. The first piece is the unstressed be- (stressed bi) that also lives in by, before, between, beneath, and below. It comes from Proto-Germanic *bi, “around, about,” from a shortened form of the Indo-European root *ambhi-, “around.” In compounds the prefix often does not add a colourful extra sense. It locates one thing with respect to another.
The second piece is the adverb hindan, “from behind.” It is built on a Germanic root hind- that also yields hinder and hindmost, plus an adverbial ending whose original force was direction from a place. On that analysis the suffix once said “from,” and the prefix supplied the idea of position: not merely motion from the rear, but location at the back of something. German hinten and Old High German hintana are close kin. The English adjective hind, “rear,” is recorded from about 1300. Some accounts treat it as a back-formation from the Old English compound; others see influence from hindan itself. The fork is left open.
The be- in this family is a part-of-speech tool as much as a meaning tool. Hind describes a rear thing. Behind attaches that rear-ness to a reference point. You can be hindmost in a line. You cannot be hindmost the house. You can be behind the house. The same pattern turns fore into before and twain into between.
Where the trail goes faint
Past Germanic the deeper source is disputed, and it is better to say so than to force a single pedigree.
General etymological handbooks often stop at a Proto-Germanic hind- of unknown origin. Other work ties the family to a distal demonstrative, a “that / yonder” stem, so that the oldest recoverable sense would be “on that side, beyond,” not “at the back.” West Germanic would then have shifted the meaning from “beyond” to “at the rear.” Gothic hindana still often means “beyond” in a geographic way, which fits that story. Competing Indo-European reconstructions exist — one via a particle meaning “beside, along,” another via a demonstrative — and none is settled. The secure part of the history remains the Germanic compound.
That uncertainty does not weaken the English account. Whatever hind- first pointed at, Old English speakers received a ready-made locator and kept using it.
Lag, secrecy, support, and a late noun
The spatial sense never left. What multiplied are figurative overlays, and they arrive at different times.
Around 1200 the word is already used for someone not as far advanced as another. That is the ancestor of falling behind in a race, in class, or in technology. From remaining after others have gone comes the idea of what is left when people depart, including unpaid obligations: wages behind, rent behind, a tenant behind with instalments. A now rare sense, still visible in eighteenth-century prose, meant “still to come, held in reserve.” Writers could speak of an enjoyment yet behind. Ordinary speech has almost dropped that use.
Secrecy is another overlay, and it is old. Late fourteenth-century English already has the idea of acting behind a person’s back, in their absence and to their disadvantage. Earlier Old English and early Middle English already contrast fair speech to a person’s face with false speech after they have gone. Theater later supplies behind the scenes, recorded in 1711 for the space at the rear of the stage; the transferred sense of private machinery, as opposed to the public show, is in use by 1779. Behind the times is nineteenth-century, from 1826.
Support is a further spatial metaphor: to have an army, a bank, or a party at one’s back. The noun for a person’s backside is late and euphemistic, dated to 1786. It is the spatial word applied to the body, not a separate root.
The origin of the word behind, then, is a built locator: a prefix that plants a reference point on a hind- element that named the rear, or, in older Germanic, the other side. English kept the back and added delay, concealment, backing, and, last of all, a polite name for the body.