1) A northern word for the water trough in which a smith cooled or 'slaked' heated metal.
It can be compared with ‘coltrough’ which served the same purpose in the Sheffield area: 1445 unum stethy de ferro … unum slek trough, York
1613 two vices the great steedye and the croked steedy … sleck troughes and other, South Cave
1638 a stythie and a slecktrough and a nayle toole, Elmswell. Slacking trough is an occasional late alternative.