Ethiopia is the birthplace of coffee: it is in the forests of the Kaffa region that Coffea Arabica grew wild. Coffee is "Bun" or "Buna" in Ethiopia, so Coffee Bean is quite possibly a poor anglicized interpretation of "Kaffa Bun". We consider Ethiopian coffees to be some of the best in the world, and extreme genetic diversity of the coffee shrub is certainly part of the reason why. Most of the coffee is either wet-processed - resulting in a vividly bright cup, with fruit and floral notes - or dry-processed with the fruit skin intact. The latter technique produces a very different, rustic fruited flavor profile, and with thicker body.
Coffea Arabica was also found in the Harar region quite early, either brought from the Kaffa forests or from closer areas around the Sudan border. It is entirely possible that slaves taken from the forests chewed coffee cherry and spit out the seeds, thus spreading it into the Harar region, through which the Muslim slave trade route passed.
Ethiopian coffees are available from some regions as dry-processed, from some regions as washed, or as both. The difference between the cup profiles produced by "natural" and washed methods is profound. Washed Sidamo, Yirga Cheffe and Limmu have lighter body and less earthy/wild tastes in the cup then their dry-processed kinfolk.
Essentially, coffee is a type of produce, and Ethiopian coffee reminds me more and more of this fact. When you find a really great coffee like the dry-processed types from the South, it is like eating Michigan peaches at the height of the season - sweet, juicy, fruity, and ripe with flavor. But then those peaches are gone, and you hope that the next season will produce the same results. Similarly, the cup profile of these coffees can be equally amazing, but when they're gone, they're gone. If all the factors line up just right, it might be the same next year. But then again, maybe not.
Ethiopian coffees can vary greatly from lot to lot. It takes a whole lot of cupping to find the specific lot of coffee that is superior to the rest. When I find the best coffee, I buy the majority of the year's production immediately, leaving a small opening in case any other good lots come along later in the season. With dry-processed Ethiopian coffee we're able to do this at the beginning of the season. These early coffees tend to be best, which is in contradiction with many other origins where the earliest are often underdeveloped.
We have many pictures and notes about Ethiopia coffee in our travelogs, namely a cupping trip to Addis and an interesting trek to Dire Dawa and Harar in the east. Since that first trip I've been back every year covering the regions in the West and South in particular - usually 2-4 times per harvest.
For wet-processed coffee, agitating the coffee in the washing channel is important to remove the mucilage.