1) Probably the same as the half- or halve-net, listed as a Scottish word in the OED with references which date from 1538.
It is considered to have a doubtful etymology but is described in one Scottish source as a bag-shaped net which could be set or held by hand to catch fish as the tide ebbs: it is said there to derive from Old Norse háfr meaning a pock-net. Yorkshire examples are: 1464-5 ‘two halvers used there’, Hull
1512-3 iiij lez sperling nettes et ij lez heryng nettes et ij le newhalvers, Hornseabeck. The second of these occurs in the will of John Skirlay, an east-coast fisherman.