For the other Scottish island, see Shillay, Monach Islands. For the Royal Navy HMT Shillay, see Isles class trawler.Shillay (Scottish Gaelic: Siolaigh) is an uninhabited island which lies 2 km north of Pabbay in the Outer Hebrides of Scotland.The name is derived from the Norse selr-øy meaning seal island and is a Scottish Wildlife Trust reserve owing to its international importance for breeding grey seals.There is no record or evidence that it has ever seen human habitation.