It’s been six years since Ben Yagoda first noticed a spike in the U.S. usage of backbencher, a term with a specific meaning in British parliamentary politics – MPs who hold no ministerial or shadow-ministerial offices and therefore are consigned to the back benches of their respective houses – and none in U.S. government, where representatives and senators sit wherever they please on their party-defined sides of the aisle. In December 2015, Ben’s UK counterpart, Lynne Murphy, anointed backbencher the UK-to-US import of the year; one of the nominators said she’d noticed that backbencher was being used in print (and some TV) “to refer to the members of a certain congressional caucus who were first elected in the elections of 2010/2012/2014, and so at this point can't all be referred to as ‘freshmen’, the usual term for first termers.”
Backbenches in Canada’s Parliament, via the very lively Parli, the Dictionary of Canadian Politics. which includes the category “Scandals, Crises, and Bon Mots”