[1] The book summarizes the results of twenty years of research of place names in the archipelagos of the Baltic Sea belonging to Finland.

The book states that during eight centuries the Swedish-speaking population in the Archipelago Sea and along the coasts of Nyland and Ostrobothnia established around a hundred thousand place Swedish names that are still known and in official use.

[1] Zilliacus describes the typical geography for island names in size order: Around islands and islets (”öar” and ”holmar”) are smaller skerries (”skär”, ”klobbar” and ”örar”), that are surrounded by rocks and shallows (”grund”, ”harur”, ”hällar”, ”kläppar”, ”kobbar” and ”blekor”, ”bådar”, ”grynnor” and ”rev”).

[1] A Hufvudstadsbladet article states that there are islands with the suffix -skär (skerry) that are large and forested, while other are barren and rocky, and thus better fit the meaning of skär as per Svenska Akademiens ordbok, the Swedish-language dictionary.

[2][3] The points on the map represent island name suffixes between Kumlinge (East Åland) and Hangö (West Nyland) including most of the Archipelago Sea such as Nagu.