When you tie this knot you will get a whiff of salt air! It was used to tie buntlines at the bottom of square sails. These were lines that ran in front of square sails to help pull the bottom up and furl them. The lines that ran on the edges of the sail were clewlines and in the middle of the sail buntlines.
When the sail needed to be furled, the bottom corners (clews) would be released and the sailors would pull on the clewlines and buntlines to pull the bottom of the sail upwards. Once the sail was folded upwards then some unfortunate soul would have to go up and tie up the sail to the spar to stop it from flopping around, but most of the pulling was already done.
The buntline hitch is getting a new life as a reliable knot to use with slippery synthetic lines.
Tying a Buntline Hitch
If you look at the fourth image of how to tie the buntline above you will recognize the clove hitch.
If you imagine that your neck is the wood rod, and the rope is a neck tie, you might recognize the knot you make to go to work. (if you wear a tie)
Its possible to finish the knot by passing the end back into the knot before it is tightened to make a loop. This makes it easier to untie.
This is a good secure knot which tends to tighten up against the wood and holds quite well. It can be used as the other end of the trucker's hitch instead of a bowline.
The buntline hitch is hard to tie under tension. It is being used in synthetic ropes because it is quite reliable and holds well.
The buntlines are shown in red on the left and the clewlines are in green in the diagram at left. They go to the mast where a block is located. The lines then go to the deck where they are fastened. The 4 buntlines are clearly visible on the sail above. Photos from Wikipedia.