“OH! My God!” exploded the young girl walking towards me in Darlington’s Post House Wynd on Tuesday lunchtime. “Ombr? is only forty quid!”

I didn’t have a clue what she was so excited about.

I turned round. She was right. “Ombr? and Balayage, £40” proclaimed a sign outside a shop.

I still didn’t have a clue what she was so excited about, but lots of other people must have understood the sign.

This is not the first time this has happened to me. In fact, in this column last week, I wrote of my visit at dusk to Coxhoe graveyard, and I mentioned as an aside how many young people there had been wandering around among the headstones looking at their phones. It was only a couple of days later that I understood those signs – they were, of course, playing Pokemon Go.

How strange, I thought. Imagine wandering around a graveyard at dusk looking at a screen while searching for Japanese-style creatures that don’t exist. How odd, they thought. Imagine wandering around a graveyard at dusk looking at headstones while searching for a man who can’t still exist because he was murdered 150 years ago.

Anyway, the ombr? sign was outside a hairdresser’s shop, which is not the sort of place I have much cause to frequent, and ombr? is a fashionable hairstyle where the colour shades from light to dark. The word comes from French where it means “to shade or shadow”, but ultimately from Latin – “ombr?” has the same beginnings as “umbrella”.

Balayage is the technique by which you come by your shadings. It apparently comes from French, meaning “to sweep”, as the hair is swept quickly through the colourant.

It is fascinating how language evolves. In some places a “sombr?” is available. This is a completely made-up word. A “sombr?” is a “subtle ombr?”, because the graduation is more gradual and presumably more expensive – it seems not yet to be available in Darlo for forty quid.

Hairdressers are not the only people introducing sweeping changes to the language. I visited the Open Treasure exhibition at Durham Cathedral this week, and stumbled across the word “feretory”. I imagined this might be a place where you kept your domesticated polecats when they weren’t fighting in a sack, but no, a feretory is “a shrine adorned with costly jewels containing the relics of a saint”, a Medieval made-up word.

St Cuthbert’s feretory is at the heart of the cathedral, although in about 1537, three of Henry VIII’s commissioners instructed a goldsmith to remove all of its jewels. They then instructed him to take a hammer to the feretory, and after a couple of blows, he shouted down to them: “Alas, I have broken one of his legs.”

Most people would have risen from the dead to protest at such ill treatment, but not Cuthbert – he clearly has the patience of a saint.

Durham is nearly unique in having a feretory – the only other that I can find is St Edward’s feretory which Westminster Abbey is built around.

The Open Treasure exhibition takes people into the 12th Century “covey”, which is next to the stunning 14th Century Great Kitchen. Here, Durham is unique. In all other parts of the country, a covey is a brood of partridges, but in the cathedral, as explained by an 1861 guide, it is “the pantry, called by ancient housekeepers the covey”.

Why? I’m not sure anyone really knows. A little cove, or bay, perhaps? But then in 1,000 years time, no one will remember why to go pokemonning means to ludicrously chase round after non-existent creatures.