Scandinavians (Swedes, Norwegians, Danes) descend from North Germanic tribes of the Iron Age (500 BC–800 AD)—distinct from West Germanic (Anglo-Saxons, Franks) and East Germanic (Goths).
Petty kingdoms merged into Denmark, Norway, Sweden by 10th–11th centuries. Viking Age (793–1066) spread genes and culture across Europe (Normandy, Danelaw, Rus').
19th-century nationalism forged linguistic (North Germanic), cultural (lagom, hygge, janteloven), political (social democracy) cohesion. Finland and Iceland often included in "Nordic"; Scandinavia proper = DK, NO, SE.