If two people are At Loggerheads they're confronting each other in dispute. In the 1400s and 1500s, a "logger" was the name of a heavy wooden block fastened to the legs of grazing horses, so that they could move slowly around a field but not jump fences or stray too far. Often, the loggers tangled with each other, which would leave the connected horses agitated and hostile to each other. The phrase passed over into wider uses after two of the main characters in Shakespeare's play The Taming Of The Shrew are seen to be "at loggerheads" with each other. However, there's a second possible origin for the phrase that dates to ancient nautical warfare. In those times, sailors used a weapon called a loggerhead, which was a long pole with a cup fixed to the end. The cup would be filled with burning tar, which would be projected at enemy ships in close quarters to create injury and fire on board. In battles in which both sides were using these weapons, they were known as "being at loggerheads".