At Loggerheads

Recorded from the 1670s, and built from an older word, "loggerhead," which by Shakespeare's time already meant a blockhead or fool (he used it that way in Love's Labour's Lost and The Taming of the Shrew). One theory says the phrase simply grew from that "quarrelling idiot" sense. A second, more specific theory points to an actual 17th-century tool: a "loggerhead" was an iron ball on a long wooden handle, heated and used to melt pitch and tar for shipbuilding, which could also double as an improvised weapon when tempers flared between workers or sailors. Both explanations are genuinely plausible and both have real supporting evidence from the period; etymologists haven't settled definitively on which one, if either alone, is the true root.