Pixies

First, a little history.
Pixies are mythical creatures found in folklore. They are said to be originating from Celtic mythology. There are other names for Pixies, such as Pixy, Pixi, Piskies or Pigsies, which is a rare occurance. Today Pixies have become more synonymous with Fairies or Sprites. This is not faithful to the original mythological Pixies, who differ in character. Pixies are generally depicted with pointed ears, often wearing a green outfit along with pointed hat. Occasionally Pixies are even portrayed with pointed eyes near the temples, which is related to the Victorian Era depiction of Pixies, and are not part of the original Pixies seen in earlier mythology.  

Discussion on their origin.
There are contrasting opinions regarding the origin of the word "Pixies". On one side it is believed to have come from the Swedish, pyske, which means “wee little fairy”. Many doubt that  Pixies are indigenous to Sweden. Others tend to be in support of the theory of Celtic origin. 

Relevant theories.
Although Pixies predate the Christian presence in Britain, the legend that Pixies are the souls of children who died before they could be baptized has become widespread. Around 1869, some were suggesting Pixies were remnants of the ancient Pictic tribes, who would paint or tattoo their skin blue, which is also attributed to Pixies. There are many variations in the mythology of Pixies.  

Depictions of these little fairies.
Pixies have been depicted in many different ways. Some Pixies are said to be very attractive, and some Pixies are said to have goat or colt (baby horse) like features. They are also said to leave behind a pixie dust that is a distinguishing feature of the popular character, Tinker Bell.  Pixies generally wear little to no clothing in many tales. Ribbons appear to be a Pixies weakness when it comes to clothing. In some depictions, Pixies are said to steal children or lead travelers astray. However, this is more in line with fairy mythology as opposed to that of the Pixies. There is a belief that much of the Pixies mythology was derived from Fairies. This could be one of the reasons why Pixies and Fairies are often used synonymously.  Pixies are also believed to fear iron since that particular metal harms them.