Muckle Holm is the name of a number of islands in Orkney and Shetland. It is an oxymoron, since muckle means "big" and "holm" refers to an islet.
Orkney Muckle Green Holm
Shetland Muckle Holm, Yell Sound, in Yell Sound between Sandwick on Yell, and Burravoe, Mainland
See also Muckle Skerry Stoura Stack Muckle Ossa