The butterfly loop is an excellent mid-line rigging knot; it handles multi-directional loading well[2] and has a symmetrical shape that makes it easy to inspect.
[3] The earliest known presentation of the knot was in A.A. Burger's 1914 work Rope and Its Uses, included in an agricultural extension bulletin from what is now Iowa State University.
[6] The authors claim to have developed the butterfly noose themselves while attempting to improve the selection of knots available to climbers.
[7] Wright and Magowan call the butterfly loop "new," along with several other of their knots, in the sense they were unable to identify any earlier record of them.
"[8] Clifford Ashley presented the knot in 1944 (text & image #1053), calling it the lineman's loop; he attributed its first publication to J.M.
(Curiously, Ashley gives no hint that this book which he twice praises contains a full knots chapter written by Drew!)