1) In a mining context, the discolouring of water.
The varied uses of this word which are commented on in dictionaries do not mention the special meaning it developed in areas where mining took place: 1779 the canker’d or rusted yellow water which is very pernicious to this land, Elland. The Huddersfield Examiner for 18 Feb. 2014 reported that the River had again turned orange and then continued: ‘the bizarre coloration has been caused by nothing more sinister than deposits of ochre from a disused mine at Jackson Bridge’. It explains a number of minor place-names, such as Canker Dyke in Huddersfield. See HPN39.