A farm name is a kind of surname used in the Nordic countries, especially in Norway.
Farm names were usually added to the given name and the patronym and originally functioned as an address rather than as a surname.
When name laws were introduced in the 19th and early 20th century and hereditary surnames became mandatory, many people decided to keep their farm name as a surname.
In Denmark many people who use a secondary patronym chose to take a farm name as a middle name.
In Dalarna, Sweden, the farm names come before the given name, e.g. Lasses Nils Jansson. The farm names are still in use in parts of Dalarna which sometimes leads to confusion in the rest of the country because they are difficult to distinguish from given names, especially as many farm names in Dalarna are exactly or almost like given names. The confusion is perfect if the farm name is like a given name of the opposite sex.
In today's automatic computer evaluations, those farm names are usually misinterpreted as given names, e.g. in the book Förnamnsboken by Sture Allén and Staffan Wåhlin, where they erroneously are listed as given names.
Farm names usually consist of words related to nature. You can find a long list of farm name elements and their meanings here.
In Dalarna, Sweden, farm names often consist of given names in the nominative or genitive form, sometimes in a contracted form if consisting of two given names, e.g. Prans (Per Hans), Knis (Erik Nils), Pellanna (Pelle Anna).