Have very limited knowledge of Welsh, but really like this song. Heard a duo do it at Wheaten Aston festival last year, but can't remember their name. Song goes something like.....
Mae nain mewn bwthyn bach
Yn y ......?
Yn byw yn bedwydd iach(?)
O bedwar ugain wed(?)
Mae pethau gandde hi(?)
Y fyddyn fechan twt(?)
A iedi ri a fuwch a gath a ci(?)
A'r mochyn yn yr cwt(?).......
and there are other verses.... lovely haunting little tune....