Ó Dónaill does not give the word "clúta" as meaning "nappy" under "clúta" or "clabhta" but an old lady in Eachléim gave me this word instantly when asked "Cén Ghaeilge atá agat ar 'nappy'?" I suspect it is related to the English word "clout" in "Ne'er shed a clout till May is out."