n my last country diary (9 January), I took readers to a portal of fairyland – a pass above Llyn y Dywarchen between Rhyd Ddu and Nantlle. I then said that the pass was called Bwlch y Moch (Pigs’ Pass). But this was wrong. Thanks to an eagle-eyed reader, I can now tell you its recent name is Bwlch Gylfin (Curlew Pass). And previous to that it was “Culfin” (Narrow Pass). Curlew Pass is an entirely apt name for an upland region of lakes and marshy bottoms, which is a perfect breeding ground for these summer hill spirits. But back to the fairies. Even a shallow acquaintance with the scholarly writings of Kathleen Raine, Oxford don Principal Rhys, WB Yeats, Marie-Louise von Franz, Marina Warner and WY Evans-Wentz will leave you with the impression of a certain maziness about the “hosts of the air” (the fairies). To join their merry dance leads to abandonment on hillsides, or waking suddenly old and in a country from which all past certainties have fled. And so it was with me when I wrote about the “fairy lady from the lake” variant folktale that locates at Llyn y Dywarchen. The fair folk are tricksters. My dictionary defined “gylfin” as “pig”. The word for “curlew” I remembered was the south Walian “cwrlin” – descriptive more of the bird’s call than its appearance. But “pig” in my dictionary was in lower case, and was therefore the Welsh word. I missed that. It translates to English as “beak”. See what I mean about maziness? And it gets worse. Why did I seize on this “pig”? Because in the Four Branches of the Mabinogion, Gwydion the Enchanter follows a herd of pigs that race into Nantlle every morning to feast on flesh and maggots which fall from the sick eagle that’s Lleu Llaw Gyffes, thus transformed after his betrayal by Blodeuedd and wounding by Gronw Pebyr. Pigs? Pig pass? From Planwydd in the Gwyrfai valley into which Llyn y Dywarchen now drains an ancient path climbs to a col just north-east of Curlew (Narrow?) Pass. Its name? Pig Pass, of course! Mazy or what? Fairies know how to confuse us mere humans. At this strange lake, you’re right by their front door. And they’re laughing at how wrong mortals can be. Dangerous, living in Wales. • Jim Perrin will be speaking from the Welsh hills with Neil McCarthy on Radio 3’s Sinking Feelings, 31 January at 6.45pm