Naut. Corrupt form of WALL-KNOT, associated with WALNUT1 1. Also walnut-knot.

1

1769.  Falconer, Dict. Marine (1780), s.v. Knot, There are several sorts of knots…: the principal of these are the diamond-knot, the rose-knot, the wall-knot or walnut.

2

1794.  Rigging & Seamanship, I. 213. A double-walnut-knot,… called a button-and-loop.

3