Words: omerta, n.

SINCE MARIO Puzo's death nobody has remarked that he figures 77 times in the OED - mostly for Fools Die rather than The Godfather, even though this contains his real legacy: "to make you an offer you can't refuse" sounds age-old, but he invented it. The new Oxford Dictionary of Idioms also misses it.

Meanwhile, Puzo's omerta is yet to appear. From the Italian for humility - or, in particular, Sicilian dialect for manliness - it is the Mafia's code of silence. This reached America early in the century, but the concept was familiar in English public schools: it is bad form to break such omerta by sneaking on other pupils' crimes. The OED's last citation of sneak comes from 1902, but it appears in Anthony Buckeridge, who merits more space.