The hide was a unit of measurement of land and value in pre-Conquest (1066) England used not just for taxation purposes but also to determine the contribution each land-holder was required to make in the event of military need.
The Domesday Book refers to the "hide". An early edition of the Encyclopedia Britannica, (1910, book 13) describes the hide as follows:
"a measure of land. The word was in general use in England in Anglo-Saxon and early English times, although its meaning seems to have varied somewhat from time to time. Among its Latin equivalents are terra unius familiae, terra unius cassati and mansio; the first of these forms is used by Bede, who, like all early writers, gives to it no definite area. In its earliest form the hide was the typical holding of the typical family. Gradually, this typical holding came to be regarded as containing 12o "acres " (not 120 acres of 4840 sq. yds. each, but 120 times the amount of land which a ploughteam of eight oxen could plough in a single day). This definition appears to have been very general in England before the Norman Conquest, and in Domesday Book 30, 4o, 50 and 80 acres are repeatedly mentioned as fractions of a hide. Some historians, however, have thought that the hide only contained 30 acres or thereabouts."
But the exact measurementrs of a hide remains unknown. "Tthe Isle of Wight contained 12oo hides" suggested one. A hide measured between 30 or 33 acres, certainly not more than 40 acres,," suggested another historian. Some references have been found to a "small hide" bnut without any reliable data so that the proposed unit can be measured and presented in modern measurements.
Again, according to the 1910 edition of the The Encyclopedia Britannica:
"There is no doubt that at the time of Domesday the hide was equated with 12o and not with 3o acres."
Chisholm, Hugh, editor, The Encyclopedia Britannica, A Dictionary of Arts Literature and General Information volume 13 (1910)