I recently listened to Karine Polwart's Dowie Hills of Yarrow, and spotted the rhyme "marrow". It is suggesting that none could be the heroine's marrow, which I assume to mean equal. The DT brings up Janet Russell's verson, where the hero, faced with nine to one odds, declares that no marrow. Again, the meaning seems to be equal, or fair.

I'm familiar with the marrer, or marrow, meaning close working partner from North-Eastern English pit usage. Digging in Mudcat, I also find it in an NE sailing context (Amphitrite), apparently the same meaning, but I don't think that's a traditional song.

I can't find the word in the Concise Oxford, and can't/won't afford a subscription to the on-line full Oxford. Can anyone expound on the origin/usage/meanings of the word?