Nikolaos is one of a very large number of Greek names with Nike, ‘Victory’, as either first or second element. The second element is Laos, ‘People’, also very common; so the union of the two was predictable. Like so many it is an optimistic name, a name of good omen. LGPN has 348 instances so far (the imminent ‘Syria’ volume will add 28 more; Egypt is still to come).
The majority of Nikolaoi are found in old Greece; there was no high profile Nikolaos to earn it the kind of broader popularity in antiquity that Alexander, for instance, enjoyed. But the most influential of all Nikolaoi is an exception. The unprepared visitor to the small town of Myra in Lycia in southern Turkey is astonished to see there numerous tourist shops with signs in Russian. But Myra was the see of bishop, later Saint, Nikolaos, said to be the most popular of all saints in Russia. In 2017, long queues formed to venerate one of his bones when it was displayed, on loan from Bari, in the rebuilt cathedral of Christ the Saviour in Moscow; Myra is a place of pilgrimage for Russian orthodox believers.
Unlike so many saints, Nikolaos was not a martyr, his story being set in fact in the time of the emperor Constantine who ended persecution of the Christians. The earliest surviving account of him is thought to go back to somewhere between 450 and the 580s (see the Oxford Cult of Saints project at http://csla.history.ox.ac.uk/record.php?recid=E05107). It tells of his successive interventions (including miraculous dream appearances, one to Constantine himself, one to a corrupt praetorian prefect) to save three generals from unjust execution. Thereafter he is credited with many and various saving interventions, on land and at sea (cf. Bicci di Lorenzo’s painting, here shown), performed during and after his lifetime: the entry listing sources for his miracles in the Bibliotheca Hagiographica Graeca extends over a remarkable twelve pages. These miracles often, like the first, had three beneficiaries: three virgins, for instance, whom he saved from prostitution by giving them bags of gold as dowries, a story thought to underly the three gold balls of pawnbrokers’ signs. Such stories of generosity are one source of his transformation, which originated in Holland and Flanders, into Santa Klaus, corrupted from Dutch ‘Sinter’, i.e. Saint, ‘[Ni]klaas’. The Oxford Dictionary of Saints writes that ‘his reputation as a thaumaturge was both cause and effect of his many patronages...children, sailors, unmarried girls, merchants, pawnbrokers, apothecaries and perfumiers all claimed him as their patron’.
Variants of the name predictably became popular throughout Europe. An early British example is Nicolas Breakspear, though he surrendered the name in favour of Adrian IV on becoming the first (and only) English Pope in 1154. The familiar spelling with an -h- was also sometimes found by the twelfth century. A feminine form is also early (though unusually the Greek original lacked a feminine): ‘Nicole or Nicola de Camville was the brave lady who defeated the French invaders at Lincoln, and secured his troublesome crown to Henry III’ (C.M. Yonge). Yonge hesitates between Nicole and Nicola because, if I understand what specialists say, Nicola too is by origin masculine (as in Italian, cf. Nicola Pisano and still today), and became feminine in some countries only because the final a recalled the Latin feminine ending. Spin-off names are very numerous: most notably, Col (an abbreviation by cutting the first syllable, whereas we typically cut the last) yielded in French a diminutive which is one source of our familiar Colin (but Gaelic Cailean through Scottish Colin is another). Why this admirable and kindly saint also lent his name to the devil is a matter for speculation: the Oxford English Dictionary has a rubric under Nick devoted to Old Nick with a first attestation from 1643, but adds ‘the reason for the appellation is obscure’.