Toponymy Erroneously, it was once assumed that Oslo meant "the mouth of the Lo river", referring to a lost name of the riverAlna. This apocryphal story is not only ungrammatical, but the name Lo is not recorded anywhere before Peder Claussøn Friis first used it in the same work in which he proposed this etymology. The name Lo is now believed to be a back-formation arrived at by Friis in support of his spurious etymology for Oslo. During the Middle Ages the name was initially spelt "Ánslo" or "Áslo" and later "Óslo" or "Opslo". The earlier spelling suggests that the first component ás might refer to the Ekeberg ridge southeast of the medieval town. The word ás with the meaning 'ridge' or 'hill' is a common component in Norwegian place names. In that case, it would read "the meadow beneath the ridge". Another interpretation could be "the meadow of the gods". The word ás with the meaning "god" is rare in place names, and Bull concludes that the name most likely has a topographical origin.
A fire in 1624 destroyed much of the medieval city, and when the city was rebuilt it was moved westwards to be closer to Akershus Fortress. King Christian IV of Denmark and Norway named the reborn city Christiania. The old site east of Aker river was not abandoned however and the village of Oslo remained as suburb outside the city gates. According to an official spelling reform the form was changed to Kristiania in 1877. The new form was used in all official documents and publications of the Norwegian State, but not by the municipality itself. The city continued to use the old form until 1897, then they also changed to Kristiania.
Change from "Kristiania" to "Oslo"
After the 1624 establishment of Christiania near Akershus fortress, the original site of the town was rebuilt and served as suburb outside the city gates. This village east of the river had preserved the name "Oslo". A 1783 map, the oldest existing of the city, uses "Christiania" for the new town west of the river, while "Opslo" is used for the easternmost settlement near Ekeberg hill. A map published in 1827 also indicates "Opslo" as the village or suburb outside the city proper. A map published by Aftenposten in 1923 labels the eastern suburb as "Oslo" and the nearby port as "Oslo harbour". After the 1859 and 1878 expansion of city borders to include the surrounding Aker municipality, the village of Oslo was included in Christiania municipality. The entire city was named "Oslo" by a law of 11 July 1924, effective 1 January 1925—a decision that caused much debate. The change was proposed in 1918 by 29 civil servants. Morgenbladet compiled a list of 28,000 signatures against the proposal. Sigrid Undset wrote that she would be ashamed if the city would try to cheat and pretend to be its predecessor on the other side of the Aker river. When the city in general now took up the name of Oslo, the eastern district of the city that had preserved the name became known simply as Gamlebyen "the Old Town of Oslo" in the borough of Gamle Oslo "Old Oslo". The old square of Christian IV's city was named Christiania torv in 1958, and this name is still in use on signs and maps. Christian IV's city with straight streets and right angles is now known as Kvadraturen and covers large parts of modern Oslo's centre, in 2009 it was proposed to rename this area Christiania. A street in Gamlebyen was named "Oslo gate" when the name Oslo still was the name of a suburb in Kristiania. The street name is still in use. "Oslo torg" is the old name for the centre of old Oslo at the intersection of Bispegata and Oslo gate, and was reintroduced by the city council in 2014.
Nickname
The city was referred to as Tigerstaden by the author Bjørnstjerne Bjørnson around 1870, due to his perception of the city as a cold and dangerous place. This name has over the years achieved an almost official status, to the extent that the 1000-year anniversary was celebrated by a row of tiger sculptures around city hall. The prevalence of homeless and other beggars in more recent times led to the slight rewording of the nickname into Tiggerstaden.
