children, especially siblings, should not argue among themselves—UK, 1818—alludes to Love between Brothers and Sisters, in Divine Songs Attempted in Easy Language for the Use of Children (1715), by Isaac Watts
(chiefly humorous): a non-specific or hypothetical person, or a person whose name is unknown, forgotten or withheld—Australia, 1902—apparently an arbitrary formation
to abandon all thought of making peace—1658—originally in the proverb ‘who draws his sword against his prince, must throw away the scabbard’ and variants
Australia, 1914—to leave indisputable evidence of one’s involvement in an affair, endeavour, etc.—‘fingerprint’: an impression made on a surface by the tip of a person’s finger, as used in criminal investigations
to engage in pointless or futile activity in the face of disaster—USA, 1969—apparently first used, and perhaps coined, by Elizabeth Carpenter, press secretary for the wife of President Lyndon B. Johnson
the principle that, where an effective legal system is absent or does not apply, brute strength and self-interested ruthlessness are what determine success, ownership, etc.—USA, 1878—predates Kipling’s Jungle book
1546—of little or no worth—here, ‘pudding’ refers to a sausage-like mass of seasoned minced meat, oatmeal, etc., stuffed into a prepared skin and boiled
the earliest occurrences of ‘feet of clay’, used without explicit reference to the Bible, date from the French Revolution (1789-1799) and translate French ‘pieds d’argile’