Source listed below.
Sherpa is the Tibetan word for "easterner". It is believed that the Sherpa people came to Nepal from eastern Tibet in the 16th century and sustained themselves through farming and yak herding. After they became officially included in the defined territory of Nepal, the northern Khumbu Sherpa were given the important task of taking goods to Tibet over the Nangpa-La, one of the few accessible routes north. In the southern region, Solu Sherpa were doing well with potato farming. In the 1950s, with the Chinese invasion of Tibet, the trade routes north were closed, however at the same time, Nepal opened its doors to westerners who were more and more interested in trekking to the highest places on Earth. Sherpas began to work for these western adventurers as porters and guides. In mountain literature, Sherpas have been portayed as everything from lazy thieves to wise mystics to expert mountaineers. Sherpas are simply a group of people who are trying to get by in a very merciless part of the world. While the trekking industry has certainly brought prosperity to many Sherpa people, many others continue to farm and herd. As you can see from the above photos, Sherpa mountaineers are now recognized worldwide for their individual feats, rather than as the "porters" for prominent westerners seeking their own glory.