One theory states that 'mara' comes from 'me-ura' meaning 'one-eyed,' a reference to the practice of blacksmiths closing one eye in order to check the iron's temperature from its color (or to an occupational hazard of blacksmiths).
「マラ」は「目占（めうら）」すなわち片目の意で、鍛冶が鉄の色でその温度をみるのに片目をつぶっていたことから（または鍛冶の職業病である）とする説