Rood has several distinct meanings, all derived from the same basic etymology

Etymology

Etymology is the study of the history of words, their origins, and how their form and meaning have changed over time.For languages with a long written history, etymologists make use of texts in these languages and texts about the languages to gather knowledge about how words were used during...

. The most significant are an obsolete English measure of area

Area

Area is a quantity that expresses the extent of a two-dimensional surface or shape in the plane. Area can be understood as the amount of material with a given thickness that would be necessary to fashion a model of the shape, or the amount of paint necessary to cover the surface with a single coat...

, an obsolete English measure of length

Length

In geometric measurements, length most commonly refers to the longest dimension of an object.In certain contexts, the term "length" is reserved for a certain dimension of an object along which the length is measured. For example it is possible to cut a length of a wire which is shorter than wire...

, and a term for a cross or crucifix

Crucifix

A crucifix is an independent image of Jesus on the cross with a representation of Jesus' body, referred to in English as the corpus , as distinct from a cross with no body....

, especially a large one displayed in a church.

Etymology

"Rood" is an archaic word for "pole", from Old English rōd "pole", specifically "cross

Cross

A cross is a geometrical figure consisting of two lines or bars perpendicular to each other, dividing one or two of the lines in half. The lines usually run vertically and horizontally; if they run obliquely, the design is technically termed a saltire, although the arms of a saltire need not meet...

", from Proto-Germanic *rodo, cognate to Old Saxon

Old Saxon

Old Saxon, also known as Old Low German, is the earliest recorded form of Low German, documented from the 8th century until the 12th century, when it evolved into Middle Low German. It was spoken on the north-west coast of Germany and in the Netherlands by Saxon peoples...

 rōda, Old High German

Old High German

The term Old High German refers to the earliest stage of the German language and it conventionally covers the period from around 500 to 1050. Coherent written texts do not appear until the second half of the 8th century, and some treat the period before 750 as 'prehistoric' and date the start of...

 ruoda "rod" (OED, "Rood"); the relation of rood to rod

Rod (unit)

The rod is a unit of length equal to 5.5 yards, 5.0292 metres, 16.5 feet, or of a statute mile. A rod is the same length as a perch or a pole. In old English, the term lug is also used.-History:...

, from Old English rodd "pole" is unclear; the latter was perhaps influenced by Old Norse

Old Norse

Old Norse is a North Germanic language that was spoken by inhabitants of Scandinavia and inhabitants of their overseas settlements during the Viking Age, until about 1300....

 rudda "club").

Measurement of area or length

Rood is an Old English unit

English unit

English units are the historical units of measurement used in England up to 1824, which evolved as a combination of the Anglo-Saxon and Roman systems of units...

 of area, equal to one quarter of an acre

Acre

The acre is a unit of area in a number of different systems, including the imperial and U.S. customary systems. The most commonly used acres today are the international acre and, in the United States, the survey acre. The most common use of the acre is to measure tracts of land.The acre is related...

 (i.e., 0.25 acre (0.1011715 ha)), or 10890 square feet or 1,011.7141056 m² (for the international inch

Inch

An inch is the name of a unit of length in a number of different systems, including Imperial units, and United States customary units. There are 36 inches in a yard and 12 inches in a foot...

) or about 10.1 are. A rectangular area with edges of one furlong

Furlong

A furlong is a measure of distance in imperial units and U.S. customary units equal to one-eighth of a mile, equivalent to 220 yards, 660 feet, 40 rods, or 10 chains. The exact value of the furlong varies slightly among English-speaking countries....

 and one rod

Rod (unit)

The rod is a unit of length equal to 5.5 yards, 5.0292 metres, 16.5 feet, or of a statute mile. A rod is the same length as a perch or a pole. In old English, the term lug is also used.-History:...

 respectively is one rood, as is an area consisting of 40 perches (square rods).

The rood was an important measure in surveying

Surveying

See Also: Public Land Survey SystemSurveying or land surveying is the technique, profession, and science of accurately determining the terrestrial or three-dimensional position of points and the distances and angles between them...

 on account of its easy conversion to acres. When referring to areas, rod is often found in old documents and has exactly the same meaning as rood.

It is confusingly called an "acre" in some ancient contexts.

Linear measure

Rood also refers to an obsolete British unit of linear measure between 16.5 and 24 ft (5 and 7.3 m). It is related to the German Rute (12.36 to 12.47 ft (3.8 to 3.8 m)) and Denmark's rode (12.34 feet (3.8 m)). The original OED

Oxford English Dictionary

The Oxford English Dictionary , published by the Oxford University Press, is the self-styled premier dictionary of the English language. Two fully bound print editions of the OED have been published under its current name, in 1928 and 1989. The first edition was published in twelve volumes , and...

of 1914 said this sense was "now only in local use, and varying from 6 to 8 yards" (or 18 to 24 ft, "Rood", II.7).