As you mention "trick or treating", if you met some Irish Children out collecting on Hallowe'en in recent years they would probably use that particular phrase, and one might be forgiven for thinking the phrase originated here. However although the practice of dressing up in costumes and masks goes back at leat 40 years here in Ireland, and I suspect a lot longer than that, the phrase trick or treat is a US import that goes back no further than the early 80s here. Someone in a recent thread on another forum cited the movie ET as the source, and the timing is about the same.

When we went out collecting our catchphrase was "Help the Halowe'en Party" - tricks never entered into it. When we collected it was mostly fruit and nuts we collected, more recently it seemed to be mostly to do with sweets, but nowadays nothing other than cash seems to be acceptable!. All of the activity was also concentrated on the night of October 31st. Lately the bonfires and fireworks seem to start in Mid September and keep going well into November.