Translation:The big saucepan is boiling on the floor.
It's a grand old Welsh song, but it doesn't make a lot of sense. Will the cat be scratching Jonny bach later?
It's an old Folk/nonsense song, Harold. Google it if you want the words. It has a really good tune: Max Boyce used to have it for his theme song. Don't worry about trying to make sense of it: Just enjoy.
Understand Welsh? It's like wrestling a bucket of snakes, isn't it? The goalposts keep moving. You have to admit, though, it is a lot of fun.
Here's a great version by Cerys Mathews at Womad 2010. https://www.youtube.com/watch?v=p-TgTPv8brI
Although there is a sense to the description if you remember that most people's houses in the 19th century were heated with coal fires with cooking being on a range around the coal fire. One of the places to boil would be on the floor of the range next to the fire:-
Thus 'sosban fawr yn berwi ar y llawr'.
Many thanks for that link! Obviously Welsh ranges were rather different from the one I grew up with in Kent, which had a hob on top for boiling and a side oven, with just a trivet at the bottom for keeping things warm. It couldn't be that the sense is subservient to the rhyme, could it? ))
I have been very slow (but then I have the handicap of not being Welsh). I've just realised this song is being referred to by Michael Flanders in his patter that introduces "The Song of Patriotic Prejudice" in At the Drop of Another Hat. Isn't it good getting the full point of a joke a mere 54 years after you first heard it?