ax to grind A private or selfish motive, a personal stake; a grievance or complaint, especially a chronic one. The phrase stems from an 1810 story by Charles Miner in which a gullible boy is duped by a flattering stranger into turning a grindstone for him. According to the Dictionary of Americanisms, the frequent but erroneous ascription of the phrase’s origin to Benjamin Franklin is due to confusion between Poor Richard’s Almanac and Essays from the Desk of Poor Robert the Scribe, the collection in which the story appeared.

a bone to pick A complaint or grievance; a point of disagreement or a difference to settle. Formerly, the expression have a bone to pick meant to be occupied, as a dog is with a bone. It was used in this sense as early as 1565. The similar French phrase uses a different metaphor, une maille à partir ‘a knot to pick.’

a chip on one’s shoulder See BELLIGERENCE.

grumble in the gizzard To complain or grouse, to be dissatisfied or annoyed. In this British expression, which dates from the late 17th century, gizzard ‘a bird’s stomach’ is applied jocularly to a human being’s throat or craw.