▁Jan j ero , ▁and ▁reduced ▁the ▁area ▁of ▁En erea ▁and ▁K aff a . ▁In ▁the ▁Gib e ▁region , ▁the ▁O rom o ▁came ▁under ▁the ▁cultural ▁influence ▁of ▁the ▁kingdom ▁of ▁K aff a , ▁from ▁whom ▁they ▁borrow ed ▁the ▁concept ▁of ▁her edit ary ▁king ship ▁( called ▁Mot i ▁in ▁all ▁of ▁the ▁kingdom s ▁except ▁Lim mu - En erea , ▁where ▁for ▁historical ▁reasons ▁the ▁king ▁was ▁known ▁as ▁the ▁Super a ), ▁and ▁the ▁practice ▁of ▁del im iting ▁the ▁boundaries ▁or ▁front ier ▁of ▁their ▁states ▁with ▁a ▁system ▁of ▁physical ▁bar riers . ▁ ▁These ▁bar riers ▁consisted ▁of ▁pal is ades ▁or ▁dead ▁h ed ges , ▁which ▁could ▁extend ▁for ▁miles , ▁separated ▁from ▁the ▁bar riers ▁of ▁the ▁neighbor ing ▁kingdom ▁by ▁a ▁neutral ▁strip ▁( called ▁mog a ), ▁which ▁was ▁left ▁un c ult iv ated ▁and ▁inhab ited ▁only ▁by ▁brig ands ▁and ▁out la ws . ▁Access ▁into ▁each ▁kingdom ▁was ▁limited ▁to ▁guard ed ▁gates ▁known ▁as ▁k ella , ▁where ▁to ll s ▁were ▁lev ied ▁ ▁These ▁kingdom s ▁had ▁an ▁economy ▁based ▁on ▁exports ▁of ▁gold , ▁civ et ▁mus k , ▁coffee , ▁and ▁slaves . ▁G . W . B . ▁Hun ting ford ▁explains ▁that ▁slaves ▁were ▁taken ▁in ▁ra ids ▁on ▁the ▁Mach a ▁tribe ▁to ▁the ▁north , ▁and ▁in ▁ra ids ▁on ▁the ▁Sid amo ▁kingdom s ▁of ▁K aff a ▁and ▁Jan j