I agree with Ariel that the blade is likely Solingen from where many blades were supplied to Ethiopia. Wilkinson of London also supplied many blades to the region.
I would discount North Africa or Arabia as point of origin as it is most unlikely that any blade from there would be decorated in the manner shown.
As to age, the blade is likely 19th or early 20th century though the date of mounting could be any time.
See here also for Ethiopian swords
http://www.vikingsword.com/vb/showthread.php?t=24493
Stu