Yes, today (12 May) is National Limerick Day, which falls on the birthday of English artist and poet Edward Lear (born 12 May 1812), who popularized the five-line humorous poetic form in his Book of Nonsense, first published in 1846. (More details here, via The Smithsonian.) As blogger and writer Richard Bist explains (see here), not all limericks are naughty. Here, for example, is limerick about the Adam Smith’s “invisible hand”:

The market appears quite unplanned,
By a hidden force that is both subtle and grand.
Though each seeks his gain,
It’s clear to explain:
They’re led by an Invisible Hand.

And here is a limerick about the “Adam Smith Problem”:

Adam Smith, two tomes did he write,
But the books made many scholars fight,
For one spoke of self-gain,
The other, of empathy’s reign,
Leaving critics to wonder who’s right!