Sources mention that it is probably of Swedish origin.
It may be of German origin, by association with Stellan Otto von Mörner, who left Branderburg for Sweden in 1597, though it is unlikely, since the name is unknown in Germany.
It may also be connected with the Old English “stillan”, meaning still, quiet, calm.
Alternative form of the name is Stelland.
Famous bearers are Stellan Skarsgård, Stellan Brynell, Stellan Olsson.