I have to say, it's a bit weird to find myself being debated on a corner of the internet dedicated to a root vegetable...
While I feel very honoured to have my website referenced on a Wikipedia article, I have to say I'm quite surprised, too, because I wouldn't have thought that it qualifies from what I understand of Wikipedia's rules about what is and isn't suitable for referencing. I do make an effort to write my articles to a decent standard and put references in, but it's not like they're peer reviewed, or anything. Having said that, I do live in Scotland, so I could point out that I am carrying on the tradition and am speaking from experience.
I didn't grow up in Scotland, but my husband did so I've spoken at length with him and my father-in-law about the practice. I can say - for what it's worth - that it's definitely rutabaga that was (and still is) used for carving the lanterns, though here they really are called tumshies, neeps, or just 'turnips'. In supermarkets you'll find them on sale as swedes, but colloquially they are rarely referred to as such in Scotland, as far as I've ever heard.
I can also say that they're an absolute bugger to carve.
Anyway, I've been unable to ascertain for certain how old the tradition is, but like some have been saying on the talk page it's not something that can be said to be particularly 'ancient' or specifically pre-Christian - especially seeing as the tumshie itself only dates from the seventeenth century. So the start of the section on Hallowe'en is incorrect when it says:
Since early times,[when?] people living in Ireland and Scotland have carved turnips and used them as lanterns to ward off harmful spirits. They are still popular throughout Britain and Ireland today at Halloween, however their use goes back to a much earlier time.This bit here:
The bonfires were replaced with hollowed out turnips (the common name for rutabaga in Ireland, Scotland. and Northern England) filled with glowing coals.
Is also a bit questionable, I think (there's also a full stop after 'Scotland' that should be a comma). The lanterns didn't replace the bonfires; in Scotland, the bonfires have arguably shifted to Guy Fawkes' night on November 5th - see Ronald Hutton's Stations of the Sun. It's true that tumshie lanterns aren't as common as they used to be, though, and most people carve pumpkins these days. Most years you'll find the odd piece in the paper about trying to revive the tumshie.
I would also say that Samhain is not a Celtic festival, it's a festival that is Irish in origin. Given Scotland's Gaelic heritage, it is also referred to as Samhain (or Samhainn/Samhainn) in Gàidhlig. It's an important distinction that needs to be made, because 'Celtic' is a linguistic term that refers to a variety of languages. It is sometimes used as a cultural term but in this context it implies that Samhain is a festival that is found in all Celtic cultures. This is not the case.
Just my tuppence worth there.
Anyway, another useful reference for you might be F. Marian McNeill's book, Hallowe'en: It's Origin Rites and Ceremonies in the Scottish Tradition. The song on page 33, called A Nicht o' Tine has a verse:
A howkit neep wi' glowerin' een
To fleg baith witch and warlock.
In other words: "A carved turnip with scowling face, to scare both witch and warlock." As far as I can tell the book was published in 1970 or 1971 - there's no date or ISBN number, but it was published by The Albyn Press in Edinburgh.
And one final thing, just to clarify: I am, in fact, a 'her'!