You wouldn’t have thought what you can learn …

J’ai appris un mot anglo-anglais pour faire des grimaçes.

… from reading an article on computer security:

The choice of a gurning picture may indicate that the worm’s writer is British. Gurning is an ancient Cumbrian practice of pulling a funny face and is famously practised in the village of Egremont at its annual crab apple fair.

I had never heard of gurning before, and neither have most of the dictionaries I checked. AMHD4 knows the word as girning (vb.: girn), and, wow, World Wide Words has an entry on it in the, er, Cumbrian spelling.

The activity it denotes is exemplified here and here — certainly topical in the context of crab apples.