Judy says:-
"In Ireland, Halloween was a good time for getting back at people you didn't like or for just plain making mischief"
The idea of a night when the rules don't apply is much more widespread in the UK than just the Celtic countries. It is probably related to the "Lord of Misrule" tradition that is part of the Midwinter festival too. It certainly fits with the Halloween- All Souls story.
I grew up in Leeds where the fourth of November was "Mischief Night"
In Liverpool there is a tradition of "Judas Fires" on that night.
There are similar customs in other parts of England, the North at least, sometimes attatched to Halloween, sometimes to Bonfire Night (November 5th)
US style Trick or Treat was unknown here until the film "E.T." set the pattern, and there is so much commercialism involved with it now, that neither purist pagans nor fundamentalist Christians have much chance of dislodging it.
It's recent, of traceable origin, but nevertheless traditional, like all those songs that trad folkies disapprove of! (see the much longer thread on Tradition!)
Cheers
Dave