A few years ago I posted an excerpt from one of the tales about Máel
The hero gives Diarmait three tufts (which normally ought to be grass)
to wipe his butt with. They turn out to be tufts of green nettle, of
thistle, and of a third unidentified plant called (in the dative)
"athrathai luaid". I recently posted this text to my blog along with
a Modern Irish translation and a photo of the mystery term from the MS:
If anyone can figure out what "athrathai luaid" is, I'd love to hear.