I just came across an interesting note in Cormac’s Glossary (tenth century) and I would like to get it down before I forget about it. The entry is as follows:
Manannan mac lir .i. cennaige amra bói aninis Manand. ise luam as deach boi aniarthar Eorpa. no fhindad tre nemgnacht (.i. gnathugtid nime) inoiret nobíd insoiniud 7 in do[i]nind 7 intan nosclæchlóbad cechtar don dá résin. inde Scoti et Brittones eum deum vocaverunt maris, et inde filium maris esse dixerunt .i. mac lir mac mara. et de nomine Manandan Inis Manand dictus est.
Manannan mac Lír: a marvelous trader who was from the Isle of Man. He was the best streersman in the West of Europe. He used to know through nemgnacht (the actions of the clouds/heavens) when it would be good weather or foul and when each of the two weathers would change into the other. Whence the Gael and the British used to call him the god of the sea: Mac Lir, Son of the Sea, and from the name Manannan is called the Isle of Man. (My translation but with respects to Whitely Stokes)
Now much of this is hardly new to anyone, but the term nemgnacht is very interesting as it only appears in one other place .i. the Cóir Anmann (‘Fitness of Names’, in Irische Texte, ed. by W. Stokes, p. 357, §156) where the passage is very nearly a quotation. It’s literally ‘cloud/heaven-action’, but it’s ringing a bell about the druids predicting the future by the clouds. The Dictionary of the Irish Language has this down as ‘meterology’, but this seems less than satisfactory … or perhaps I am wishing for more than is here.
I will have to come back to this later.