"salt works, salt pit," Old English, apparently a variant of wic "dwelling place, town" (see wick (n.2)).
Examples from the Web for wich
The Secretaries wuz apinted, and then the committees—two on each from the South and one from the North, wich wuz consiliatin.
Wat wuz the sence uv our askin our people to vote for Kernels for Congris wich hed, doorin the war, drafted their sons?
These two instances, I beleeve, is the only ones in wich I hev ever hed to say farewell.
If ye hask me, wich (which) ye don't, then no wisky, says oi; and if ye hask why?Black Rock|Ralph Connor
I have lost a great dele of my cloaths, and I am thinking of drawing of about six pound, wich I think I can make shift with."The Gallant, Good Riou", and Jack Renton|Louis Becke