‘Name a “masquerade-adjacent business”,’ said my husband, looking up from the London Review of Books. I don’t know where he got the copy. We don’t have it delivered.

He was reading a review of a book about masquerades. That chimed with a thought I had last Saturday: that Halloween is becoming a fancy-dress day, not always related to the dead – or not dead-adjacent, as the suddenly popular formula would have it. The Guardian opined: ‘It wouldn’t be Halloween without some kind of Trump-adjacent costume.’

Adjacent used to have a taste of officialese about it. It also featured in a novelty song by Danny Kaye, declaring: ‘The square of the hypotenuse of a right triangle is equal to the sum of the squares of the two adjacent sides.’ The concept ‘adjacent’ does not appear in the Greek of Euclid’s Proposition 47, where the adjective is περιεχουσων, ‘containing’. Good old Adelard of Bath (1080-1152) just made it the duobus reliquis, ‘remaining two’ sides.

The vogue use of -adjacent, as the second element in a compound, originally denoted a physical closeness to the thing specified by the first element. The Oxford English Dictionary picked up a phrase from 1882: ‘Jericho-adjacent Worcester’ (the Oxford college).

Used figuratively, the closeness is one of likeness: the Guardian recently referred to Wallsocket by Underscores as ‘a sprawling, rock-adjacent concept album’.

That meant ‘resembling rock’. But the meaning drifts. It can also mean ‘-themed’. But someone in the Telegraph, on the subject of Celebrity Race Across the World, wrote of ‘four pairs of fame-adjacent adventurers’ – ‘nearly famous’, or ‘almost famous’. Discussing frying-pans, the Sun became playful: ‘Hard anodised means a harder, denser surface than standard non-stick aluminium, so it takes metal-adjacent abuse better and warps less on a mega-hot hob.’ It must have meant ‘metal-related’.

The tone of these formulations is generally jocular. They lie in the same territory as not unadjacent to (found since the 1960s) or not 100 miles from (in use since the 1820s). Now the encounters are closer.