1) A set of vessels for table use, typically of pewter. A complete set was for twelve people.
1408 ‘one dozen vessels of peutre garnish’, York
1434 halfadosan garnyssht de peuter vessell, Campsall
1488 In uno garnysh vasorum electri, xs, Beverley
1535 Item ij garneche of puder vessell, Stillingfleet
1568 Item pewther vessell in the Custodye of Alice Roodes, twoe garnishe lacking thre pecis, Healaugh.
2) Money extorted from a new prisoner, either as a jailer’s fee or as drink-money for the other prisoners (OED).
1659 Payd for garnish by Jno Ireland upon the recipts of the prisoner 1s, Sowerby
1721 at the garnishing of a prisoner he sels his ale, tho’ bad, for six pence per quart ... everybody that comes to the garnish, York.