The Bourchier knot was the badge of Henry Bourchier, Earl of Essex, d.1483 [HB 99]. The knot was used by subsequent members of the Bourchier family, sometimes substituting other items (thorn branches, garters) for the cords [Siddons II.2 94].
The modern term “granny knot” is drawn as a Bourchier knot. For heraldic purposes, the “square knot” and “reef knot” are equivalent to the Bourchier knot as well.
Kemrith Danil bears as a badge: Argent, a Bourchier knot vert.