Bakker Bugle Blog Say it three times fast. In Luxembourgish.

From the best word-a-day website, at wordsmith.org:

serein

PRONUNCIATION:
(suh-RAN [the second syllable is nasal])

MEANING:
noun: Fine rain falling from an apparently cloudless sky, typically observed after sunset.

ETYMOLOGY:
From French serein, from Old French serain (evening), from Latin serum (evening), from serus (late).

USAGE:
“She must have caught a chill from the serein, that’s all!” Raphael Confiant; Mamzelle Dragonfly; Farrar, Straus and Giroux; 2000.

Here in Dublin, I’ve observed serein during the morning, afternoon, and evening as well. I don’t know of any uniquely Irish slang for this type of rain, although there are lots of words and colloquial phrases for heavier rain.

There must be a word for serein, given how common it is here (and how uncommon it is everywhere else I’ve lived).