WE’RE all familiar with the concept of the earworm; it’s a wonderfully apt and descriptive word for a piece of music that gets lodged in your head and which, not matter how hard you try, you can’t shake off.

My dad, for many years from the mid-1960s onwards, would sing Donald Where’s Yer Troosers by the Scottish McWarbler Andy Stewart.

It was so much of an earworm for him that he would just belt out the first line or so and then we all knew that the rest was just circulating around his mind like water surging around a central heating system in a house.

At some point when I was a child his Andy Stewart earworm morphed into Puppet on a String by barefoot song-wrangler Sandie Shaw and there was a brief period when the two earworms seemed to live happily in his head side by side when he sang a medley of the two, so that Donald seemed to have lost his puppet on a string.

Earworms, eh? You just can’t control them.

Recent earworms that have taken up residence in my thinking chamber include the first couple of lines of that hippy classic Alone Again Or by that great band Love and, at the other end of the musical and cultural scale, the theme tune of the Beverley Hillbillies.

I’m waiting for the moment when, like Stewart and Shaw, they merge so that Arthur Lee from Love is singing about Texas Tea.

My latest earworm is a curious one, and one that I don’t think will catch on nationally, which is probably a good thing. It comes from the fact that when I’m with my two-year-old (he’ll be three soon!) grandson Louie we like to sing about anything.

Of course singing is great and it’s always good to sing and that goes without saying, or it goes without singing.

So a couple of months ago we were in the kitchen and we were making up songs about everything and everything. There was a verse about a ladle and a verse about a pan and there was a verse about a banana and there was a verse about a carrot.

Then, as they do, that song ended abruptly and another song began.

There was a pause, as there always is, before the next song began as we decided, like we always do, what to sing about.

Think of it as that moment when they conductor lifts their baton before the orchestra plays a note, or when the band glance at the set list to try to work out what the heck they’re playing next because the set list is scribbled in a fading pen and it’s at the far side of the stage away from the glare of the lights.

We glanced at the calendar next to the sink; it’s a series of views of Dumfries and Galloway and I always say that it must be Photoshopped because it isn’t raining on any of the pictures.

The picture Louie and I were looking at was of a ruined castle and so we began to talk about why the castle was ruined and from somewhere, (like Jed Clampitt striking oil) the idea of Charlie the Castle Crusher was born.

I imagined that the castle hadn’t just fallen down, it had been crushed by bad old Charlie. Louie liked that idea and so of course we made a song up and the song instantly became an earworm that’s been living with me rent free ever since.

The words are simple and yet, though I say so myself, profound: ‘Charlie the Castle Crusher, crushing castles all day long. Charlie the Castle Crusher, singing his castle crushing song. He’s crushing castles every morning, crushing castles every night, he’s crushing castles in the evening. Crushing castles is his delight…’

A masterpiece, don’t you think? Well, Louie does. And I do. It’s hard to convey the bouncy tune in print but somebody said it sounded a bit like a minor key version of Rudolph the Red-Nosed Reindeer, which is fairly accurate.

But now I can’t stop singing it! Walking down the street, waiting for a bus, sitting in the house reading, I suddenly come out with Charlie the Castle Crusher.

It’s a true earworm.

And Louie sings himself to sleep with it, so that’s nice. All together now: ‘Charlie the Castle Crusher…’