People at “loggerheads” are considered to be confronting each other. In the 15th and 16th centuries a ‘logger’ was the name given to a heavy wooden block fastened to the legs of grazing horses, enabling them to move slowly around a field but not to jump fences or stray too far. Frequently the loggers tangled with each other, leaving horses connected at close quarters and becoming agitated and hostile to each other. The phrase passed over into wider uses via Shakespeare’s play The Taming Of The Shrew, during which two of the main characters are seen to be at ‘loggerheads’ with each other.
There is a second possible origin for the phrase dating to ancient nautical warfare. Sailors used a weapon called a loggerhead, which was a long pole with a cup fixed to the end. These were used to project flaming tar at enemy ships in close quarters to create injury and fire onboard. Naturally both sides used similar weapons and such battles were known as ‘being at loggerheads’.