What is a Viking? A ferocious plunderer and pirate from the pagan North creeping up on innocent monks and hapless peasant women? Or a low-ranking oarsman on a ship? In other words: Where does the epithet stem from? What might it mean? And who used it?
For a very long time this has been a hotly disputed question, and at least six different understandings have been put forward since the 19th century.
1) Already in 1852 it was claimed that the word Viking(r) stemmed from the feminine Vík (Bay). The argument was that the Vikings would seek shelter in bays, hence the name accorded to them.
2) But perhaps the first Vikings came from Vi(kin) – the Norwegian Skagerak Coast? It stands to reason that this idea has been especially pushed by the Norwegians, who in the beginning of the 20th century (and following their hard-won independence from Sweden) sought to monopolise the Nordic Vikings.
3) Maybe the word was derived from the verb vika, in the sense withdraw, leave (as soon as they had laid their hands on the booty)? This explanation was voiced already in 1840
4) From a feminine Vík, derived from the verb vík(j)a, with the meaning deviation, detour. A Viking would thus be a person who made a detour from home
5) Closely connected to this understanding is another explanation, whereby the word Viking also stems from vík(j)a but in the meaning ‘a man who makes a journey abroad’.
6) Finally it may stem from the Old English wīcing from the verb wīcian, ‘to lodge, camp, encamp’. This word is documented rather early. It would mean that the Old Norse word is a loan-word from Old English.
In a very interesting philological survey  from 2005 of the whole field (from which this overview is taken), carried out by Eldar Heide from Bergen University College, these different suggestions have been explored one after the other. This is not the place to present a summery of this very detailed, but immensely interesting work.
At any Viking voyage the shifting of rowers must have been a dominant feature, writes Heide. Even after sails were introduced, the navigation of the ship demanded an effort from the rowers to keep it steady. However, it is important to note, that this also fits very well with the fact that the word stems from the Migration period, when ‘viking’ probably just meant any man who went on a voyage together with his comrades in a rowing boat. According to Heide, It may even be that the first ‘Vikings’ were the seafaring immigrants from Angel, Saxony and Friesland, who rowed across the North Sea to England and conquered the island for the second time (first time was Caesar). This was the kind of ship, which the excavations at Sutton Hoo revealed.
Interestingly enough, this also fits very well with the findings by Judith Jesch , who published a detailed study in 2001 on the use of the word víkingr and the concept fare i Víking, both found on Runic Stones and in skaldic verses from the 10th and 11th centuries (that is in the late “Viking Age”).
According to her work the noun Víkingr primarily referred to a person and was essentially used as a personal name. Thus there are fifteen inscriptions on runic stones, where a person is named Viking, while there are only three runic inscriptions where víkingr is used as a common noun. One is enigmatic, another is clear enough, but what it might mean, is not well understood. The last one of these from Bro in Uppland might be understood as a commemoration of a man, Assur, who was guarding ‘uikika’ – Vikings. Perhaps he was on a ship-watch guarding the professional oarsmen (slaves or peasants), which must have been an increasing part of any crew in the later Viking Age (10th and 11th centuries). Perhaps, par-pro-toto, the inscription  tells us that he was guarding the rowing benches of the ship. Normally though, such a bench was called a þopta (ON) or þofte (OE).
“These last three inscriptions are thus the shreds of contemporary evidence that people, whom we might call ‘Vikings’ also called themselves something similar”, she writes (p. 49), moving on to discuss the three instances on runic stones, where the word is used as an abstract noun in connection with ‘I’, where persons had either been or had died ‘I víkingu’.
Finally she analyses the word as used in a number of skaldic verses. Here she concludes that the use is mainly pejorative, suggesting that víkingr was primarily applied to opponents. However, she finds no sign of the use of the word with any ethnic connotations. A meagre harvest, we might say.
To conclude with Heide and (perhaps) Jesch: Víkingr did not at all seem to be an ethnonym used by either the Northmen themselves or their victims. Vikings were oarsmen, who went sailing (rowing) – either as part of war-bands, trading expeditions or on pilgrimages. Some of them might even have been mighty rowers, thus earning the nickname ‘Víkingr’. But according to the skaldic verses from the tenth century, this was not in itself a very worthy occupation. In this world the real heroes were the drengr , which has been amply demonstrated by Judith Jesch.
Pertinent is perhaps that the traditional Viking ships at this point had grown into bulk-carriers. Perhaps they were partly manned by plain troopers, aka vikings? This might also partly explain why the víkingir were perhaps more than anything looked down upon in the late Viking period (10th and 11th centuries), when kings and other magnates were bent on state-formation  and wished to exert at least some control of what had now become thought of as low-life pirates continuing to operate in the shallow waters of the peripheries of the Nordic world.
Finally – but only mentioned as a fundamentally unprovable hypothesis – we might understand the massacred victims from Ridgewell Hill as exactly such a group of Vikings; a sorry collection of desease-ridden low-lifes, working as oarsmen rowing ships across the North Sea and per chance caught in a skirmish down in Dorset, where some soldiers in the army of Aethelred succeeded in taking their ship. Perhaps Assur , who was commemorated in Bro in Uppland by his wife, died while defending the Vikings – oarsmen – who found their grave in Ridgewell Hill.
We shall never know…
 Víking – ‘rower shifting’? An etymological contribution.
By Eldar Heide
In: Arkiv för nordisk filologi 2005, vol. 120, pp. 41 – 54
Vikingen – Roddaren
By Bertil Daggfeldt
In: Fornvännen 1983, vol 78, pp. 92 – 94
 Ships and Men in the Late Viking Age: The Vocabulary of Runic Inscriptions and Skaldic Verse
By Judith Jesch
Boydell & Brewer 2001
 The inscription on the Runic Stone from Bro in Uppland (dated to 1013 – 1055) goes like this:
kinluk × hulmkis × tutiR × systiR × sukruþaR × auk × þaiRa × kaus × aun × lit × keara × bru × þesi × auk × raisa × stain × þina × eftiR × asur × bunta * sin × sun × hakunaR × iarls × saR × uaR × uikika × uaurþr × miþ × kaeti × kuþ × ialbi × ans × nu × aut × uk × salu
Old Norse transcription:
Ginnlaug, HolmgæiRs dottiR, systiR SygrøðaR ok þæiRa Gauts, hon let gæra bro þessa ok ræisa stæin þenna æftiR Assur, bonda sinn, son HakonaR iarls. SaR vaR vikinga vorðr með Gæiti(?). Guð hialpi hans nu and ok salu.
“Ginnlaug, Holmgeirr’s daughter, Sigrøðr and Gautr’s sister, she had this bridge made and this stone raised in memory of Ôzurr, her husbandman, earl Hákon’s son. He was the viking watch with Geitir(?). May God now help his spirit and soul
 From Viking Stronghold to Christian Kingdom. State Formation in Norway, c. 900 – 1350.
By Sverre Bagge.
Museum Tusculanum Press, University of Copenhagen 2010.
Christianization and the Rise of Christian Monarchy: Scandinavia, Central Europe and Rus’ c. 900–1200.
Ed. by Nora Berend
Cambridge University Press 2007
What’s in an ethnonym? Theories on the word `Viking’
A debate from a Corner of the 10th Century Europe hosted by Jonathan Jarrett
Runic Stone from Bro in Uppland, Sweden. Source: Wikipedia
The small rowing boat in the photo is a replica of one of the small Gokstad boats, built in Roskilde in 2013 and launched in 2014