I remember living in St Petersburg FL in the 60s when the news paper had big headlines exhorting all to beware! the Terrible Williamsons were sweeping into town. Don’t let anyone you don’t know resurface your driveway or fix your roof! etc. I remember my neighbhood being inundated with these fix-it people going door to door and sometimes while the householder was answering the front door someone else was going in the back door.
The Celts invaded the British Isles and were contested by somebody. I doubt its was elves, fairies and leprechauns!