Until the Middle Ages, people in Sweden were identified by one name only. Family names were seldom ever used until the 1600's.
By the end of the 17th century, the nobility, merchants, etc., were using family names.Their names were often Latinized by the clergy, changing them with "i" or "ius" endings, sometimes using the Latinized name of a place.
Farmers and laborers used the patronymic system. This system shows that a person was the son or daughter of a certain man. For example, Karl, the son of Sven Larsson, would be called Karl Svensson. Hannah, the daughter of Sven, would be called Hannah Svensdotter.
In the 1860's, people started using a permanent surname. Gradually the people used their father's patronymic as their surname. Thus, Karl would become Karl Larsson, Hannah would become Hannah Larsson. The children of a family would not necessarily make the change at the same time, so you must be careful in identifying a person.
An immigrant to Sweden would usually retain their foreign (i.e. native) surname, which was passed down.
In birth records one cannot tell what the last name of the child is, so be very careful when following a person through the records.
To avoid confusion, men were given military names when they entered the service. These were often short names which may pertain to the military, such as; Svard (sword); to trees, such as Bjork (birch); to animals, such as Hjort (deer); etc. Children might or might not use their father's military name. Sometimes several of the children would use the military name and some the patronymic name. Thus, Petter Johansson Elf's children could take either Pettersson, Johansson, or Elf as their surname.
After he left the military a man might continue to use his military name, or he might return to his patronymic.
On a soldat torp (tenant soldier's small holding) the name stayed with the farm, so people living at that place (note: who assumed the name of the "torp") are not necessarily related.
To change one's name it was only necessary to inform the minister, who would write the new name in the church records.
Women continued to be identified by their maiden names after marriage.
There were no rules for surnames for illegitimate children. A child may have the patronymic name from the father's first name or the father's surname, or the matronymic name from the mother's first name or the mother's surname. The last name may not be shown in the birth records, but can usually be found in later records, such as the clerical survey, or when a person leaves home or gets married.
You may find a surname in a family spelled many ways in different records. Rules for spelling were much less rigid in the earlier times than they are today, and people used whatever spelling appealed to them.
First names may also vary in spelling for the same person, such as Katrina, Catrina and Katarina. Sometimes you may find a name such as Christina or Kjerstin in the birth records and later find the same person being called Stina. Lars may be Lasse; Magnus may be Mans; Anna may be Annika; Johanna, Hanna or Anna; Helena, Lena or Helen; etc. Check the birth date and other information to be sure you have the right person.
Sometimes people moving from a rural area to a big city changed their names in order to appear more city-like. They would choose names with endings such as ____berg, _____strom, often combined with the name of their former home or parish.
Many emigrating Swedes changed their names upon arrival in the United States. They may have taken a family military name, which was often translated into English, when arriving in the U.S. or at a later date. The name change was often done by just using a different name, with no legal transaction as would be required today. Another practice was to include the name of the farm or village in Sweden as part of the American name.
It was often the custom to give a newborn child the same name as that of a child that had died. There were various other customs in different areas. One of those was to name the first boy and girl after the father's parents and the second boy and girl after the mother's parents, the next child after the father's grandparents, and the next after the mother's grandparents, etc. There were, however, many exceptions to this custom.
The first law governing names was passed in 1901, when everyone was encouraged to choose a permanent family name. However, a few people still use a patronymic, but must get permission from the government to do so.