"salt works, salt pit," Old English, apparently a variant of wic "dwelling place, town" (see wick (n.2)).
Online Etymology Dictionary, © 2010 Douglas Harper
Examples from the Web for wich
It hides so much, my Polly; wich I'm sure, my dear, you'll twig!
Wich the paper is one as a gent who is reelly a gent can enjoy.
Wich they couldn't take me for a Paddy or 'umbugging "Out of Employ."
If ye hask me, wich (which) ye don't, then no wisky, says oi; and if ye hask why?Black Rock
Wich we aren't as sweet as iersons, not yet as fresh as paint!