The name Onmoraki was reportedly created by adding words 'in' (negative) and 'oni' (ogre or ghost) to a monster 'mara' that hindered Buddhists from attaining enlightenment, to put stress on the meanings of ogre and monster, while another theory has it that it was a mixture of 'Onmo' meaning obstacles and 'Rasetsuten' (Rakshasa, an evil spirit).
陰摩羅鬼の名の由来は、仏教で悟りを妨げる魔物の摩羅（魔羅）に「陰」「鬼」の字をつけることで鬼・魔物の意味を強調したもの、もしくは障害を意味する「陰摩」と「羅刹天」の混合されたものとの説がある。