The French name for Lake Geneva (Lac Léman, also called Genfersee in German) dates back to Celtic times. It meant "water between the mountains". The Romans then named it "Lacus Lemanus".
Not everyone agrees with this version of the story, however. Here's another version: In 63 B.C. the Greek geographer Strabo observed that the lake had been called "limnê" for centuries, which simply meant "lake" in Greek. The Gallo-Romans transformed this "Limnê" into "Lemanus". Designations such as " Lake of Lausanne ", used in the Itinerary of Antoninus (2nd Century) or "Lake Geneva", from the time of the Reformation, appeared only at a much later stage. However, the inhabitants of Vaud and Savoy always referred to " Lake Leman ". From 1798 to 1814, the lake gave its French name to the département of Léman, which comprised the territories of Gex, Geneva and northern Savoy .
With a total surface area of 582.4 square kilometres (348 in Switzerland and 234 in France), the lake is 72.3 kilometres long, from Geneva to Villeneuve, and averages 10 km wide (minimum width 8 km, maximum 13.8 km). Its maximum depth is 309.7 metres and it has 167 km of coastline. Its surface is 372.3 metres above sea level in summer and a metre lower in winter. The water is clear to a depth of 6.5 to 7.5 metres, depending on season and location.
The lake is divided into three zones: the Petit-lac (the narrowest part, from Geneva to Nyon); the Grand lac (the whole of the widest part between Lausanne and Evian) and the Haut-lac (the part delineated by Vevey-Montreux-Bouveret-Thonon). The Rhône, which alone is responsible for draining 18% of Switzerland's waters and supplies the bulk of the lake water, joins the lake at Villeneuve. The second source of lake water is the Dranse, on the French side. Other significant rivers include the Venoge and the Veveyse.