"salt works, salt pit," Old English wic, apparently a specialized use of the wic that means "dwelling place, town" (see wick (n.2)).
Entries linking to wich
wick n.2
"dairy farm," now surviving, if at all, as a localism in East Anglia or Essex, it was once the common Old English wic "dwelling place, lodging, house, mansion, abode," then coming to mean "village, hamlet, town," and later "dairy farm" (as in Gatwick "Goat-farm"). Common in this latter sense 13c.-14c. The word is from a general Germanic borrowing from Latin vicus "group of dwellings, village; a block of houses, a street, a group of streets forming an administrative unit" (from PIE root *weik- (1) "clan"). Compare Old High German wih "village," German Weichbild "municipal area," Dutch wijk "quarter, district," Old Frisian wik, Old Saxon wic "village."