Kaffir

The term was originally an Arabic word meaning non-believer or infidel; and in this role it could be simply descriptive or derogatory, depending at least in part on the point of view of the speaker. (The same word, spelled with one ‘f’, was used to denote certain people in NE Afghanistan who were not included in the early medieval wave of conversions to Islam; but their descendants have in the main been converted and therefore do not like being called by this name.)