The Guanches were the original inhabitants of the Canary Islands
. The word Guanche is a corruption of "Guan Chenech" which means "Man from Chenech" or "Man from Tenerife
." This term eventually came to refer to the people from any of the islands, not just Tenerife.
Though ancient writings make reference to a few ancient explorers encountering the Canary Islands (often by accident), the people of the islands remained almost totally isolated, even from each other, until the Spanish "discovered" them in the fourteenth century.
Their isolation is one of the great mysteries of the Guanches. Living on relatively small islands with lots of big trees around, they somehow managed never to invent sailing. Which begs the question: "How did they get there in the first place?" One theory is that they sailed there, (maybe Berbers from North Africa?), along with their domesticated animals, and then somehow forgot how to sail. Or maybe they were left there by another seafaring culture? Hoping to establish a colony? Umm... Most of the theories are pretty weak and there isn't much evidence for any of them. As for why they didn't sail once they were on the islands, it was probably because of the same strong currents and trade winds that kept everyone else away, until the improved navigation technology of the Age of Exploration made the Canaries accessible.
Anyway, when the Spanish found them each island had developed its own dialect (though a dialect of a language previously unencountered), lived mostly as shepherds, and could be classified as neolithic in terms of technology. When the Spanish decided to conquer, it wasn't much of a contest (though it did take them about 100 years to do it). Those Guanches who weren't killed were baptized and made subjects of the Spanish crown, their names were changed and they were made to speak Spanish. The Guanche language(s) and way of life disappeared very quickly.
You can still find traces of them in many of the place names of the Canaries, however, and in the large numbers of tall, blonde, blue-eyed people there.