Orcadian dialect is a dialect of Insular Scots, itself a dialect of the Scots language. It is derived from Lowland Scots with a degree of Norwegian influence from the Norn language, which is an extinct North Germanic language. Orcadian is spoken in Orkney, north of mainland Scotland.
The other Insular Scots dialect is Shetlandic, which shares some features with Orcadian.
References
Orcadian dialect Wikipedia(Text) CC BY-SA