This week the supreme court ruled that the government’s prorogation of parliament had been unlawful and so was “void and of no effect”. Lexically, the kerfuffle was most interesting for the surge in popularity of the hitherto obscure word “justiciable”.

Justice, from the Norman French justicer, was originally a verb as well as a noun, meaning to bring to trial or to punish. (From Latin ius: a right or law.) What was “justiciable”, from the 15th century, was what could properly be decided at court, or what was subject to a particular jurisdiction. Crimes on the high seas, 19th-century legal scholars wrote, were “justiciable” only in the country to which the vessel belonged, and so forth, and the people it was proper to try in courts were themselves called “justiciables”.

The government had argued that its decision to prorogue was not justiciable because it was an exercise of its prerogative power. The supreme court, as though speaking to a child, reminded it: “The courts have exercised a supervisory jurisdiction over the lawfulness of acts of the Government for centuries.” Court-watchers will be eager to discover whether, in due course, Boris Johnson personally might become a justiciable.