Latin, ferlang, ferdingus
As units of assessment, furlongs occur mainly in circuit 2, in the counties of Cornwall, Devon and Somerset, being one-quarter of a virgate, or a sixteenth of a hide.
For more detail, see the note to DEV 1,4 in Domesday Book, vol. 9: Devon, edited by Caroline and Frank Thorn (2 vols., Phillimore, 1985), which can also be found online at: https://hydra.hull.ac.uk/resources/hull:535.
See also quarter.