The world's tallest mountain has three names — and the Western one is the newest
Tibetans and Nepalis had names for the mountain long before a British survey named it after a man who never saw it — and who objected to having it named after him at all.
Chomolungma
"Goddess Mother of the World" — the Tibetan name used for centuries, long before Western surveyors reached the region. Used officially in China today (珠穆朗玛峰).
Sagarmatha
"Forehead of the Sky" — adopted as Nepal's official name in the 1960s, used in Nepali government and educational materials.
Everest
Assigned in 1865 by the Royal Geographical Society, at the suggestion of British Surveyor General Andrew Waugh, who named it after his predecessor Sir George Everest.
George Everest didn't want the mountain named after him. He argued that local names should be used wherever they existed, and reportedly objected that his own name couldn't be written or pronounced correctly in Hindi or other local languages. The Royal Geographical Society adopted the name anyway, since no single local name had yet been standardized in Western records at the time.
Today, Nepali and Chinese climbing permits and government documents use "Sagarmatha" and "Chomolungma" respectively; "Everest" remains the name used in most English-language and international contexts.
Sources: Royal Geographical Society historical records; Nepal Department of Tourism; official Chinese geographic naming standards. Country shapes: Natural Earth.