Prehistory and origin of Stockholm
According to the Chronicle of Eric, written in the 1320s, Stockholm was founded by Birger Jarl around 1250 as a lock to the Lake Mälaren region ("laas fore then sio", "lock before that lake") in order to prevent pirates from reaching the seven cities and nineteen parishes around it. Another medieval source ("Visbyannalerna"), however, claims the city was founded in 1187 following a pagan pillaged the city of Sigtuna, and as there was an "Earl" named Birger around at that time too, the disputed origin of the city are likely to remain obscure and some historians choose a diplomatic interpretation saying there was some sort of fortification around by the mouth of lake Mälaren when the city was founded during the second half of the 13th century. As Snorri mentions no city in his account but some sort of fortification called a "kastali" (in various manuscripts curiously said to be located east and west of "Stocksund"), it has generally been assumed this fortification eventually developed into the castle Tre Kronor located where still is the Stockholm Palace.
Stockholms nation
Stockholms nation is a student society and one of thirteen nations at Uppsala University. The nation has its origins in the mid-17th century and regards 1649 as its official date of foundation, although this is uncertain. A document in the archives mentions students enrolled in the nation in 1649, but this is a copy of an original that was lost in a fire in 1702, and the nation is mentioned in the protocols of the consistory (board) of the university from 1656 as having been in existence for three years, which would put the foundation date at about 1653.