vikingyoudaoicibaDictYouDict[viking 词源字典]
viking: [19] There are two competing theories as to the origin of the word viking. If its ancestry is genuinely Scandinavian (and Old Norse víkingr is first recorded in the 10th century), then it was presumably based on Old Norse vík ‘inlet’, and it would denote etymologically ‘person who lives by the fjords’ – a logical enough notion. However, earlier traces of the word have been found in Old English and Old Frisian, from around the 8th century, which suggests the alternative theory that it may have been coined from Old English wīc ‘camp’ (ancestor of the -wick, -wich of English place-names).

On this view, the term originated as a word used by the Anglo-Saxons for the Norse raiders, who made temporary camps while they attacked and plundered the local populace. It was introduced into modern English at the start of the 19th century as an antiquarian’s or historian’s term.
[viking etymology, viking origin, 英语词源]
Viking (n.)youdaoicibaDictYouDict
Scandinavian pirate, 1801, vikingr, in "The History of the Anglo-Saxons" by English historian Sharon H. Turner (1768-1847); he suggested the second element might be connected to king:
The name by which the pirates were at first distinguished was Vikingr, which perhaps originally meant kings of the bays. It was in bays that they ambushed, to dart upon the passing voyager.
But this later was dismissed as incorrect. The form viking is attested in 1820, in Jamieson's notes to "The Bruce." The word is a historians' revival; it was not used in Middle English, but it was reintroduced from Old Norse vikingr "freebooter, sea-rover, pirate, viking," which usually is explained as meaning properly "one who came from the fjords," from vik "creek, inlet, small bay" (cognates: Old English wic, Middle High German wich "bay," and second element in Reykjavik). But Old English wicing and Old Frisian wizing are almost 300 years older than the earliest attestation of the Old Norse word, and probably derive from wic "village, camp" (large temporary camps were a feature of the Viking raids), related to Latin vicus "village, habitation" (see villa).

The connection between the Norse and Old English words is still much debated. The period of Viking activity was roughly 8c. to 11c. In the Anglo-Saxon Chronicle, the raiding armies generally were referred to as þa Deniscan "the Danes," while those who settled in England were identified by their place of settlement. Old Norse viking (n.) meant "freebooting voyage, piracy;" one would "go on a viking" (fara í viking).