Is this a plural word? Is there a singular word that means one item of clothing?
Yes, éadaí is plural; éadach is its singular form.
"Clothing" is also accepted. (April 6, 2015)
I have a feeling that knowing the etymology of this word might give me some helpful mnemonic cause for some reason I just cannot get this specific word to settle into my head properly.
The singular form éadach comes from Old Irish étach.
Try the pronunciation A D and it's easy to remember
Nice thought, but what ties “A D” to clothing? (I had the same idea, but used the number “80” to indicated the number of outfits my wife has. Sadly, that could also apply to the number of pairs of shoes she has, so it might add to my confusion.)
easy pronunciation: 'AD'/'80'