Whereas most of its placenames have a straightforward provenance from Old Norse, the meaning of the name Orkney itself is rather more hard to decipher. It is known that the islands around 200BC were referred to as 'the isles of the Orc' from the writings of an Irish king, Labrail Loingceach. The islands are again mentioned in the Irish annals around about 250AD as 'Orc'. This word is Irish Gaelic for 'pig', and it was adapted by the invading Norse as it sounded so akin to their word for seal örkn. If you have ever visited Orkney , you will know how very common these mammals are around the shorelines of the islands. In placename studies of anywhere, this taking of a word from one language and changing its meaning beacuse the two distict words sound similar is very common.

orkneyjar has a very good section on placenames