Surviving
nooses in the United Kingdom show simple slipknots that were superseded in the late 19th century with a metal eye spliced into one end of the rope, the noose being formed by passing the other end through it. The classic hangman's knot was largely developed in the United States, the heavy mass of the knot intended to crush blood vessels in the neck and if tightened beneath the jaw, to lever the head to one side. Filmed hangings of war criminals in Europe after
World War II, conducted under US jurisdiction, show such knots placed in various places, including at the back of the neck.
Each additional coil adds friction to the knot, which makes the noose harder to pull closed or open. When
Grover Cleveland was the sheriff of Erie County, he performed two hangings. Cleveland was advised by a more experienced Sheriff to grease the rope with
tallow and run it through the knot a few times to ensure rapid closure with the drop. The number of coils should therefore be adjusted depending on the intended use, the type and thickness of rope, and environmental conditions such as wet or greasy rope. Six to eight loops are normal when using natural ropes. One coil makes it equivalent to the simple
running knot. (Wikipedia)