Something beginning with 'N'

Today's limerick:

Said Jill, ‘Whatever’s the matter, Jack?’
As he dropped his pail with a clatter back
Down in the well:
‘There’s no need to yell,
Toads are harmless: it’s only a Natterjack.’

I may have said it before, but never mind: the Limerick is unusual in English verse forms in being almost entirely accentual; most forms are accentual-syllabic. That is to say, provided the 3-3-2-2-3 pattern of stress is kept to, it doesn't really matter how many syllables you squeeze in. However, the following really won't do:

There was an old man of Thermopylae
Whose limericks didn't scan properly.
When they said it was so
He replied 'Yes, I know;
I just go all to pieces with the last line.'