Chomolungma
In 1856, the mountain was "discovered" by the British, who named it after the person who had "gained a reputation as the most ill-tempered sahib in India". Of course, the Tibetans and Sherpas had known it was there all along, and called it Chomolungma. Later, the Nepalese invented the name Sagarmatha (brow of the sky) to remind everyone that they owned half the mountain. I'll follow the Tibetans.
The meaning of "Chomolungma" seems to be lost in time (it doesn't mean Goddess Mother of the Universe/Earth/World/Snows/whatever).
Tenzing Norgay's mother (a Tibetan) once translated it as "the mountain so high that no bird can fly over it".
When asked what it means, a Tibetan nomad answered:
"Hen."
"Hen?"
"Yeah, but a big hen, with all its feathers puffed out. So it looks fat."
"Big fat hen?"
"Yes, big fat hen."
Source: Everest, Summit of Achievement.