The story
The OED, mentioning the variant forms stose, stoce, stowse, and stow, says it is "of obscure origin; possibly a contraction of stothes pl. of stothe" i.e. stooth; however, compare stow.
Etymology from Wiktionary, CC BY-SA 4.0.
stowce
Today it means: A windlass, a device for drawing ore up from a mine, also formerly used (when made entirely of wood) to indicate possession of mining land. Full definition →