Oidhche Shamhna — the Eve of the feast of Samhain in Gaelic tradition and Halloween in English — is upon us again, though in the midst of a pandemic we might not see soo many samhnairean or “guisers,” known in North America as “trick-or-treaters.”

There’s plenty of debate about the origins of trick-or-treating customs, with some arguing the tradition was invented in the US fairly recently ...