Wikipedia
In Old Norse sources, such as sagas and runestones, Særkland or Serkland was the name of the Abbasid Caliphate and probably some neighbouring Muslim regions.
Despite the obvious similarity to Saracen, the place-name is likely derived from serkr (gown, modern Swedish "särk") and land (land, country), referring to the clothes of the people who lived in the area.
Notably one of the Ingvar Runestones, the Gripsholm Runestone, raised circa 1040 at Gripsholm, commemorates a Varangian loss during an ill-fated raid in Serkland. The other remaining runestones that talk of Serkland are Sö 131, Sö 279, Sö 281, the Tillinge Runestone (U 785) and probably the lost runestone U 439. For a detailed account of such raids, see Caspian expeditions of the Rus.
Several sagas mention Serkland: Ynglinga saga, Sörla saga sterka, Sörla þáttr, Saga Sigurðar Jórsalafara and Hjálmþés saga ok Ölvis. It is also mentioned by the 11th century skald Þórgils fiskimaðr, and the 12th century skald Þórarinn stuttfeldr.