1) A term for small or refuse coal, recorded from <i>c</i>.1440.
A witness in a case that had to do with the ‘dilapidation’ of the parsonage in Whitkirk, in 1683, blamed the vicar Mr Dade who had allowed coal to be extracted from ground underlying the church, and Coal, slack and rubbish to accumulate above ground. Slack was sometimes taken as fuel to nearby works: 1773 13 load of sleck for furnish, Elsecar
1775 18 Load of Sleck for Brick Makers 9s or used to back-fill quarries, along with other colliery waste: 1792 carry away into the quarry or stone pit … all the sleck, earth and rubbish from the pit hills. The dialect spelling ‘sleck’ was very common.
2) A hollow, depression, or shallow area between two stretches of rising ground.
1205-11 et inde per la slake super Brokthornes usque ad Blakmore, Gisburn
1331 at Ryehill in le Slak ... ˝ an acre, Marske in Cleveland
1541 a great stone erected and set up in the myddest of a peat mosse or slacke, Wibsey
1562 ther was some grene gresse that growed in some slackes, Rawdon
1697 one half day-work in the slack of the field, Holmfirth. The turnpike records for the Keighley to Bradford road contain: 1755 An account of the slacks filling and hills lowering, from the Two Laws to Toller Lane.