Definition of "fortnith"

[…] to Anne Mercer, my daughter, the some of xiiij li., according to an agrement between her husband and me, to be paid within one fortnith of the death of my wiffe.

1631 January 2, John Hutchinson, The Will of John Hutchinson‎, Knaresborough; republished in Wills & Administrations from the Knaresborough Court Rolls […] (Publications of the Surtees Society; 110), volume II, Durham: Andrews & Co., 1905, page 119

[…] & palmson fare which is kept the thursday before palme sunday all in the towne, & this fare setts all the fortnith fares for the year Round.

a. 1731, William Storr, Book of Remarkes‎, page 23; republished as “The Book of Remarks of William Storr, of Scalm Park, 1678-1731”, in W. Consitt Boulter, editor, The Yorkshire Archaeological and Topographical Journal, volume 7, London: The Yorkshire Archaeological Society, 1882, page 53

To dark is still used in Swaledale (Yorkshire) in the sense of to lie hid, as, 'Te rattens [rats] mun ha bin darkin whel nu [till now]; we hannot heerd tem tis last fortnith'.

1873, Richard Morris, Walter William Skeat, “Glossarial Index”, in Specimens of Early English‎, volumes II: From Robert of Gloucester to Gower, A.D. 1298—A.D. 1393, Oxford: Clarendon Press, page 490