As regards the prohibition on the utterance of the fairy…

““As regards the prohibition on the utterance of the fairy name by mortals, either that of the species as a whole, or of individuals, it his undoubtedly issued from sources exceedingly ancient. It is implicit in animistic belief that the name of a man or spirit is a vital part of the individual. In some remoter areas of the world a person's name is still regarded as being equally vital or important with his spirit or soul, and to know it and pronounce it presumes power over the person or spirit to whom it belongs. Supernatural beings in general are indeed exceedingly touchy upon the subject of their names being freely bandied about, and to this rule fairies are no exception. It is for this reason that the fays have bestowed upon them such alternative titles or sobriquets as 'the good neighbours,' or 'the wee folk.' 'We find,' says Wentz, 'that taboos of a religious and social character are as common in the living fairy-faith as exorcisms. The chief one is against naming the fairies.' 'Gin ye ca' me fairy / I'll wark ye muck Ie tarrie [trouble],' says an old Scottish rhyme which popular belief put into the mouths of the elves. 'The fairies,' remarks Robert Chambers, 'are said to have been exceedingly sensitive upon the subject of their popular appellations. They considered the term 'fairy' disreputable.””

— Lewis Spence