I think the first time I saw this word it was in the context of being a term of contempt – something like the old besom or the little besom or whatnot. I didn’t really know what it meant or where it came from; I thought, “Well, it must be something negative.” I guessed the pronunciation correctly – it’s like “beezum” – and imagined it might be like a sort of busybody who drops abuse in over the transom.
Well, the first thing to know is that if you call someone a besom, that someone has a bosom. Yes, the term, when applied to a person, is a disparaging term for a woman. But literally it’s a word for an implement. It just happens to be an implement associated with women, historically.
No, I don’t mean a distaff. But, though calling a woman a besom is not calling her a witch, you will often see a besom in a picture of a witch. Though women got to spin rockets (originally a word for a spinster’s implement), they didn’t get to ride them; they rode brooms instead – and the brooms you’re most likely to see pictured are besoms: bundles of straw or twigs wrapped around a staff.
Of course, now Harry Potter rides one too, when playing quidditch. But they call them brooms. Never mind; besom just isn’t all that common a word anymore – perhaps partly because we have better kinds of broom. In some Scots dialects, though, besom remains the generic word for a broom. In mainstream English, it has long been little used – see the Google Ngram comparison.
One may imagine that with a broom you sweep a room while with a besom you can just be busy like a bee. The sounds are different, anyway; though they both have the /b/ to start with, broom has the rumbling /br/ that you also get in brush, and then it gets into the even more thundery /um/, while besom has the high front /i/ sound and then a buzz and a bump before at last landing back at the same /m/ as in broom – the nasal version of the stop that began the word. I do think /brum/ is more reminiscent of a sweeping motion than /bizəm/ is, but I don’t know whether that had any influence on their respective popularity.
So where are you most likely to encounter this word, other than nowhere? You will find figurative uses of it in the King James version of the Bible (“I will sweepe it with the besome of destruction”) and in Shakespeare’s Henry VI Part 2 (“Be it known unto thee by these presence, even the presence of Lord Mortimer, that I am the besom that must sweep the court clean of such filth as thou art”). You will also find literal uses of it in assorted literature, but not much that was written after the mid-1800s.
You may also find it in the company of other words: a besom-head is a blockhead; a besom-rider is a witch; besom-heath is heath used to make besoms (fancy that), and besom-weed is the same thing – or that other similar plant with which besoms may be made. What was that plant called? Oh, yes: broom.