owsern.
Apparently a misreading of ouse (see ooze n.1).
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society > occupation and work > materials > derived or manufactured material > leather > leather-making materials > [noun] > tannin > tanning solutions
sumac?a1350
bark-waterc1440
oozea1450
owser1704
sour1756
souring1777
tan-pickle1820
gambier1853
kassu1862
tan-liquor1882
tan-ooze1901
1688 R. Holme Acad. Armory iii. 350/2 A Tanners Pooler, or Poler..is..to stir up the Ouse, or Bark and Water.]
1704 Dict. Rusticum at Pooler It is an Instrument used about Tanners Pits, wherewith they stir up the Ouser [1726 Owser], or Bark and Water.
1715 J. Kersey Dict. Anglo-Britannicum (ed. 2) Owser, the Bark and Water, in a Tanner's Pit. [Also in later dictionaries.]
This entry has been updated (OED Third Edition, March 2005; most recently modified version published online December 2020).
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n.1704