According to a theory presented in the 1630s, at the time of Swedish colonisation of coastal areas of Finland, colonists from Hälsingland in central Sweden had arrived at what is now known as the Vantaa River and called it Helsingå ("Helsinge River"), which gave rise to the names of Helsinge village and church in the 1300s. This theory is questionable, because dialect research suggests that the settlers arrived from Uppland and nearby areas. Others have proposed the name as having been derived from the Swedish word helsing, an archaic form of the word hals (neck), referring to the narrowest part of a river, the rapids. Other Scandinavian cities at similar geographic locations were given similar names at the time, e.g. Helsingør in Denmark and Helsingborg in Sweden.
When a town was founded in Forsby village in 1548, it was named Helsinge fors, "Helsinge rapids". The name refers to the Vanhankaupunginkoski rapids at the mouth of the river. The town was commonly known as Helsinge or Helsing, from which the contemporary Finnish name arose.
Official Finnish Government documents and Finnish language newspapers have used the name Helsinki since 1819, when the Senate of Finland moved itself into the city from Turku, the former capital of Finland. The decrees issued in Helsinki were dated with Helsinki as the place of issue. This is how the form Helsinki came to be used in written Finnish. As part of the Grand Duchy of Finland in the Russian Empire, Helsinki was known as Gelsingfors in Russian.
In Helsinki slang, the city is called Stadi (from the Swedish word stad, meaning "city"). Hesa (short for Helsinki), is not used by natives of the city.Helsset is the Northern Sami name of Helsinki.