Ask And It Shall Be Given
I am reading Collapse by Jared Diamond, and although the book could have used a copy editor and a serious pruning — it's easily too long by a quarter — it is overall a fascinating read.
One sentence that gave me pause was
More certain evidence of northwards exploration is a cairn at latitude 73°N containing a runestone (a stone with writing in the Norse runic alphabet), which states that Erling Sighvatsson, Bjarni Thordarson, and Eindridi Oddson erected that cairn on the Saturday before Minor Rogation Day (April 25), probably in some year around 1300
for which I had to jot down the reference because I realized that, not being Catholic, I had no idea what "Minor Rogation Day" is, or Major Rogation Day, or any other day of rogation, or even what exactly rogation might be.
I had certainly run across the word before. There is a chapter in a book I adore, The Joy of Bad Verse (seriously, buy it, because it will enrich your life in ways you can hardly imagine), about Alfred Austin, dreadful British poet laureate, who wrote among other bad poetry a verse-play, England's Darling, about King Alfred, which contains the lines (which I had unwittingly committed to memory)
ALFRED: Now name me this.
EDGIVA: Milkwort, or gang-flower.
ALFRED: Which the learned call rogation-flower.
Naturally, you are thinking, "This Alfred sounds like a real jerk," and you are right. But I had never actually stopped to wonder what rogation-flower was (that's a picture of it up there: pretty, isn't it?), or how it had come by its name (among the learned, anyway), or what that name referred to.
Last things first, as usual. If you look at "rogation" and think about where you might have seen it or something like it before, it will eventually occur to you that it is the second half of the word "interrogation", and therefore "rogation" might have something to do with asking questions. And that is just what it is. It comes from the Latin "rogare", "to ask"; rogation days are days in the ecclesiastical calendar specifically set aside to ask God for mercy, and the rogation-flower is as Edgiva noted milkwort, which has white, blue, or pink flowers, and is so named because garlands of it were traditionally made and used on rogation days.