1) Probably clouds on the peaks and sides of the moors, specific to West Yorkshire.
On 26 August 1786 the Rev. John Murgatroyd wrote in his diary: A fine day – some little moorgrime, Slaithwaite. The most likely meaning is that there were clouds on the peaks and sides of the moors, an explanation given in the Sheffield Independent in 1864. It was only in west Yorkshire that Wright found the term.