What is "val-d'oise"

Val-d'Oise is a French department, created in 1968 after the split of the Seine-et-Oise department and located in the Île-de-France region. In local slang, it is known as "quatre-vingt quinze" (i.e. "ninety-five") or "neuf cinq" (i.e. "nine five"). It gets its name from the Oise River, a major tributary of the Seine, which crosses the region after having started in Belgium and flowed through north-eastern France. Paris-Charles de Gaulle Airport, France's main international airport is partially located in Roissy-en-France, a commune of Val d'Oise.