The sign of the relieved canine

I've just re-read Interesting Times by Terry Pratchett in which he makes a (to me) delightful reference to his days as a sub, before he introduced a grateful public to the delights of Discworld.

Interesting Times is set in a fantasy version of medieval China, complete with complex pictograms. One of his characters is puzzled by an oft repeated pictogram that seems to show a dog urinating.

As any sub of my advancing years would recognise, Mr P is sharing an in-joke with with the likes of JD and I because 'dog's cock' is time-honoured engine-room slang for an exclamation mark.

Good to see the great man hasn't forgotten his roots!