at loggerheads. : in or into a state of quarrelsome disagreement.

What is loggerhead slang for?

noun. a thick-headed or stupid person; blockhead.

Where does the expression loggerhead come from?

loggerhead (n.)

1580s, "stupid person, blockhead, dunce, numbskull," perhaps from dialectal logger "heavy block of wood" + head (n.). Later it meant a type of thick-headed iron tool (1680s), a type of cannon shot, a post in the stern of a whale-boat, and a type of turtle (1650s).