Generic Amharic term for foreigner, meaning mainly westerners. The word is really a corruption of the germanic term Frank. Similar corruptions can be found throughout a zone stretching from Ireland in the west to Malaysia in the east. The word has more or less followed the French throughout their colonial adventures.
Although the country itself it was never colonised, the French presence in Djibouti led to contacts with Ethiopia. Use of the term in Amharic was probably introduced no earlier than the middle of the 19th century. It may have found its way into Amharic by way of the Greek "frangi" and the Egyptian "farangi." Another theory holds that is was derived from "Ferenchi" which is itself a corruption of the English "French" or "Frenchie" since the British had interests in nearby Yemen and it probably stems from a time when both English and French were filtering southwards through the Sudan. The latter theory is linguistically less sound though. The first British invaders of Afghanistan were also given the label "ferengi."
The Star Trek series features an alien race of stereotypical money-grubbing, misogynistic traders called the Ferengi. Use of the name Ferengi in Star Trek may not be entirely coincidental, as there is a hint of an Ethiopian theme surrounding the Ferengi.
Thanks to Gritchka for helping check out the linguistics and to Apollyon for the Afghan angle.