The Kalmyk loop is named after the Kalmyks, a nomad ethnicity in Russia. It is relatively easy to tie, it is secure, and it undoes quickly when pulling the free end.
Used by Mongolian herders and bushcraft enthusiasts as a general purpose quick release loop.
Quick release. After heavy loading the knot may become jammed but usually it is relatively easy to loosen it.
When tightening the knot make sure it is dressed properly. If the knot is loaded before it is snugly dressed the knot may collapse.
Without the quick release the knot is known as Cossack knot or Eskimo bowline.