To the Celtics, the bonfire represented the sun and was used to aid the Druid in his fight with dark powers. The term bonfire comes from the words "bone fire," literally meaning the bones of sacrificed animals, sometimes human, were piled in a field with timber and set ablaze. This practice of burning humans was stopped around 1600, and an effigy was sometimes burned instead.

Legends tell us that on this  night, all the hearth fires in Ireland were extinguished, and then re-lit from the central  fire of the Druids at Tlachtga, 12 miles from the royal  hill of Tara.

Householders were levied a fee to relight their holy fire which burned at their altars. The extinguishing of the fires symbolized the "dark half"  of the year, and  the re-kindling from the  Druidic fires was  symbolic  of  the returning life hoped  for, and brought about.