We welcome back Merrill Perlman, who writes the "Language Corner" column for Columbia Journalism Review. Just in time for the holiday season, Merrill takes a look at the origins of some yuletide expressions.

A couple of years ago we discussed some of the abuse that poor, misused apostrophes suffer this time of year, in expressions like "seasons' greetings," "'tis the season," and "be good for goodness' sake."

This year, your holiday gift is a discussion of some seasonal expressions and their origins.

Let's start with the "mas" in "Christmas." Since that's a combining form of "Mass," "Christmas" literally means Christ Mass." And Christmas isn't the only "mas." If you're familiar with the British or with British authors, you've probably heard of Michaelmas (celebrating St. Michael) or Candlemas (the feast of the purification of the Virgin Mary).

Then there's "yuletide," in the song "Have Yourself a Merry Little Christmas," among other places. People who equate "Yule" and "Christmas" may be surprised to hear that "yule" was originally a midwinter pagan festival for Scandinavians and Anglo-Saxons. (Its Old Norse word was jōl.) In the days before Julian calendars, the early forms of "yule" also referred to specific winter weeks. Most dictionaries prefer it lowercased, but you'll see "Yule" as often as "yule" in print. The "tide" combining form is just an old way of saying "time." (Like "yule," it's really old, recorded in the first century A.D.)

You might have — or bake — a "yule log" for the holidays. The Oxford English Dictionary, which calls it a "yule-log," traces its first use to 1725: "from its being burnt as an Emblem of the returning Sun." Though it was originally a large log burned in fireplaces especially for Christmas, someone decided to make a pastry out of it. Foodtimeline.org says its origin is French (it's often called a Bûche de Noël, literally "hunk of yule wood"), probably from the nineteenth century, based on the ingredients. (All yummy.)

On your mantle you might also have a "poinsettia" plant. Note that last "i," which is frequently forgotten — after all, most people pronounce it "poin-SET-ah," not "poin-SET-tee-ah." This tradition is not so old: Poinsettia plants, native to Central America, were not introduced into the U.S. until 1828 when Joel Roberts Poinsett, the U.S. minister to Mexico, brought them home.

The poinsettia's association with Christmas is also traced to Mexico, where they're known as flor de noche buena, or holy night flower. In a Mexican legend, a young girl on her way to a Christmas Eve service, sad that she had no offering, met an angel. The angel told her to pick some ugly weeds and offer them instead. When the girl placed the weeds on the altar, they burst into bloom.

Of course, those bright red (or white, or pink) blooms are not flowers at all, but bracts — the leaflike part that usually surrounds a flower. The poinsettia's flower is very small, the yellow or red berry-like things in the middle of those bracts.

And despite what you may have heard, poinsettias are not poisonous. Some people are allergic to its sap, but the leaves themselves taste so bad that few people would be tempted to eat them anyway.

Consider that your Christmas tip.