Before the Conquest, a reeve (Old English ġerēfa; similar to the titles greve/gräfe in the Low Saxon languages of Northern Germany) was an administrative officer who generally ranked lower than the ealdorman or earl. The Old English word ġerēfa was originally a general term, but soon acquired a more technical meaning.
Land was divided into a large number of hides—an area containing enough farmable land to support one household. Ten hides constituted a tithings, and the families living upon it (in theory, 10 families) were obliged to undertake an early form of neighbourhood watch, by a collective responsibility system called frankpledge.
Tithings were organised into groups of 10, called hundreds due to containing 100 hides; in modern times, these ancient hundreds still mostly retain their historic boundaries, despite each generally now containing vastly more than a mere 100 families. Each hundred was supervised by a constable, and groups of hundreds were combined to form shires, with each shire being under the control of an earl. Each unit had a court, and an officer to implement decisions of that court: the reeve. Thus different types of reeves were attested, including high-reeve, town-reeve, port-reeve, shire-reeve (predecessor to the sheriff), reeve of the hundred, and the reeve of a manor.
The word is often rendered in Latin as prefectus (Modern English prefect), by the historian Bede, and some early Anglo-Saxon charters. West-Saxon charters prefer to reserve the term prefectus for the ealdormen (earls) themselves.
After the Norman conquest, feudalism was introduced, forming a parallel administrative system to the local courts. The feudal system organised land on a manorial basis, with stewards acting as managers for the landlords. The Norman term describing the court functionary—bailiff—came to be used for reeves associated with lower level courts, and with the equivalent role in the feudal courts of landlords.