Latin was the major language of record through the medieval period in Britain, and as a result there is a wide range of surviving documentary sources, many of which have been transcribed, edited, and published.

From Anglo-Saxon England we have a body of charters issued by kings and others, which survive in the original, in later medieval cartularies, or in copies made by early modern antiquarians. The land survey and valuation in the Domesday Book provides an unparalleled picture of the land conquered by the Normans, its owners and its resources. Thereafter, England developed into one of the most notable medieval bureaucracies, with the great government departments of the Chancery and the Exchequer producing extensive documentation covering all aspects of the government not only of England, but of Wales, Ireland, Scotland (during the periods of English rule there), the Channel Islands, Normandy, and Gascony. All of these are reflected in the Dictionary, as are minorities within England, such as Jews or Huguenots.

Many of these documents — the Pipe Rolls, the Patent Rolls, the Close Rolls, and the Gascon Rolls, for example — have been published, at least in part, and these published documents have been extensively excerpted for the DMLBS. For those that remain unpublished, our first editor Ronald Latham, formerly Assistant Keeper of the Public Records, was able to use his wide knowledge of the material in the Public Record Office (now part of the National Archives) to provide us with invaluable evidence excerpted from the manuscript sources. Others with inside knowledge have been similarly helpful.

For Scotland we have been less fortunate and have to rely much more on printed sources. Medieval Scotland was a much smaller country than England, and its government was therefore less formal and bureaucratic, so the sources are fewer, but useful publications include the regesta of several kings of Scots (David I, Malcolm IV, William I, Robert I, David II), the Exchequer rolls, and the acts of the Scottish parliament.

For both kingdoms and their various dependencies there are also large numbers of documents from sources other than government. Monasteries, cathedrals, boroughs, lordships, churches, universities, and other institutions generated documents, and many of these collections have been studied and edited, often by local record societies like the Surtees Society and the Oxford Historical Society. These give us wills, court records, formulae for letters, land surveys and a wide range of other material.

These very varied documents have been an especially rich source of material for study and this is particularly true from a lexicographical perspective. This is an area where the Latin language is particularly flexible and productive of new words. Anglo-Saxon charters tend to be written in a high style, full of orotund phrases, complex syntax, and learned vocabulary. Words like cunctigena, protoplastus and solicola are typical. For most of our period, however, documentary Latin is a practical working language, where style takes second place to function, and indeed the writers may not have had a formal literary education. Classical Latin words are passed over for new forms, structures are simplified or improvised, and vernacular words are either Latinized or imported wholesale (often with the telltale preceding le which indicates a word in the vernacular, whether French or English). These can have many sources — words derived from Old and Middle English, Scots, Anglo-Norman, Welsh, Irish, Scots Gaelic, Cornish, Old Norse, Gascon, Hebrew and other languages such as Spanish or Italian can be found. Sometimes which vernacular is favoured can be surprising: for example, for the word noutegeldum (neat-geld, manorial rent paid in cattle) forms deriving from the Old Norse naut are more common than those from the Old English neat.