Orinally brought to Brazil in the 1500's by Bantù slaves from Africa and used to accompany the famous dance called Capoeira (it's a sort of a martial art were two fighter are trained while berimbau, tambourine and agogo bells play a rhythm).

Berimbau was also a mean of communication used by slaves to prevent to be understood by their bosses and is considered a sacred instrument.

Is made by a wooden arc (a special kind of wood called Biriba), a wire from end to end and a gourd (cabassa plant) opened on one side (resonator) attached with a piece of cord at the lower side of the arc (20cm from the bottom).

Moving the gourd back and forth from the abdomen creates a kind of wah-wah effect. You also can vary the "feel" of each sound.
To play berimbau You need a stick to strike the wire, a stone or a coin which is held against the wire and one ore more caxixi.

Basically, there are three different sound:

Moving the gourd back and forth AND changing the position of the coin allows you to create slides between the different notes. The berimbau is also a great instrument to experiment w/.

First example of berimbau pattern and key notation:

CREDITS
Thanks to Lars for providing part of the above info.