The main objective of this study was to identify, describe, and explain selected instances ofrngrammaticalization in Ethiosemitic languages and Oromo. Body part terms, similatives,rndemonstratives, and allatives are the major topics considered in the study. Body part termsrnare observed grammaticalizing into markers of spatial, temporal and logical relations. In thernNorth Ethiosemitic languages the Semitic root msl is found developing into a comitative andrntemporal marker. The evolution of similatives into complement, temporal, and purpose clausernmarkers is also observed in the majority of Ethiosemitic languages and in Oromo. The wordrnfor ‘one’ (and) is proposed as an alternative etymology for the Amharic similative markerrnÇndä. Relative and genitive markers are analyzed with a demonstrative origin as a commonrnsource. The genitive-relative element yä- is treated as a result of polygrammaticalization fromrna common demonstrative element.