What is the origin of the word scandinavia

1765, from late latin scandinavia, skandinovia, a mistake for scadinavia, from a germanic source (compare old english scedenig, old norse skaney "south end of sweden"), from proto-germanic *skadinaujo "scadia island,"

The name “scandinavia” originally referred to the former danish region of scania(currently part of sweden). the word was then used in the late 18th century and was introduced by the early linguistic and cultural scandinavist movement meaning that it referred to the kingdoms of denmark, norway and sweden.