The first Vikings were Scandinavian fishermen and farmers who spent most of the year at home then ventured across the sea in the summer. A local leader would summon them each summer to go on raids starting around 700 AD. They would also seek out new people to trade with and be on the look out for new lands they could settle.
One explanation for the term viking is that it referred to "a seaman who came from the Vik district of Oslo fjord". The Old Norse had the term vikingr which could mean a freebooter, sea-rover, pirate or viking. That led the term to be synonymous with Scandinavian pirate. When they were going off on a pirate raid that meant they were "going viking". That was in line with the Old English term wicing that meant "a Scandinavian sea raider". During their raids the Vikings set up temporary camps and wic was a term for village or camp. It was also related to the Latin vicus which meant village.
Their foundation was also intertwined with their mythology and legends. First there was the Völsunga saga around 436 which had the hero Sigmund who was followed by his son Sigurd the dragon slayer. The epic poem about the Viking hero Beowulf was penned around 520. King Hadding and King Hrólfr Kraki were two legendary kings of Denmark whose stories both contain many supernatural references.