A limerick has a rhyme scheme of aabba. I have learned since Verse and Adversity's limerick fest that the beat is called anapestic, three syllables of weak-weak-strong, which sounds like this: da-da-dum, da-da-dum…
The classic limerick is 3 such groups or feet in lines 1, 2, and 5; with two feet in lines 3 and 4.
Illustrating that scheme is this classic limerick by Edward Gorey:
Said a girl who, upon her divan
Was attacked by a virile young man:
"Such excess of passion
Is quite out of fashion!"
And she fractured his wrist with her fan
So what makes a beat 'weak' or 'strong'?
If it is an emphasized word or syllable, it is strong. You can usually tell by saying it, but the dictionary may help when it's unclear. That isn't the final answer though, as the way people actually pronounce words is often not what the dictionary indicates, and you have wiggle room to use whichever works better. This goes further, in that a word like 'missed' can be legitimately rhymed with 'list' and can therefore count as one syllable.
The Limerick Discussion Page suggests 'one good test is whether the sentence sounds natural with beats on the assumed accented syllables. A particular one syllable word may be weak or strong depending on the context…The preposition, "of" can be strong in iambic, e.g. "I am the leader of the street", but is nearly always weak in anapestic, e.g., "I'm the king of the road".' This site also gives general rules for words of one, two and three syllables - I urge you to check it out if this form interests you.
There are permitted variants in meter, making it easier to write a limerick, but a bit more confusing at first. One such variant allows the first group or foot in a line to omit one beat and be weak-strong or da-dum. This makes for the well known:
There was a young lady from Kent
type of limerick. Here is one written by Elvenesse from the limerick thread at HASA that consistently uses the da-dum in the beginning of every line:
The mirror of Galadriel
Is set in a small wooded dell
The visions you see
When in it you pee
I beg of you, please do not tell.
This limerick not only had perfect adherence to rhyme scheme, it is also a great example of the kind of humor demanded by the Limerick Discussion Page: "A good limerick must have some element of the absurd." One web site quoted E. V. Knox (past editor of Punch magazine)as saying a limerick should "contain the largest amount of improbable incident or of subtle innuendo that can be crowded into the available space."
A limerick Tay wrote on the same thread varies the initial beat pattern, with lines 1 and 4 having a single initial weak beat, and lines 2, 4, and 5 having two initial weak beats:
Prince Imrahil, Knight of the Swan
has a part that, though sketchily drawn
will be sorely missed
if it doesn’t exist
when Return of the King is put on
This one has good rhythm, but some critics would say it suffers from being too clean - no innuendo or outright naughtiness.
Another accepted variation is one or two extra weak beats at the end of a line, but the rhyming lines must be consistent about this; unlike above, where variation at the beginning sounds fine even if it isn't consistent through the rhyming lines.
Here is one Nessime wrote with one trailing weak beat at the end of lines 3 and 4.
I've a bone of contention to pick
with PJ and his Two Towers flick:
Hasufel had to settle,
tho' he was in fine fettle;
his part lost to some movie-verse shtick.
And one of mine with one trailing beat after lines 1, 2, and 5.
Mariel who at times wrote fanfiction
was distraught at the strength of addiction
She developed a stash
of h/c, angst and slash
Surely this is a grievous affliction!
This next has two weak trailing beats on lines 1, 2, and 5:
To discuss Elessar and virginity
I have found a most nat'ral affinity
Was he pure as the snow?
Please describe blow by blow -
we'll ignore Evenstar's consanguinity.
This one was inspired by a discussion in the Sexuality in Middle-earth forum about virginity. It cheats a little - the first line is off because the stress should be on the second syllable of Elessar, but to keep the rhythm it has to be on the third. In the second line I have also cheated, but since many people do not enunciate the middle syllable of 'natural' it still doesn't sound too bad. Although I suspect the really good limerick writers would not stoop to this, clever rhymes can distract from other defects.
Some examples of delightful rhymes from the Limerick thread: kindred/inbred, Smeagol/Deagol/illegal, audacious/salacious/ bodacious and one that I found especially impressive - imperial/Lothiriel. I can overlook a lot of small fudges for rhymes like these.
This all sounds fairly complicated, and a perfectionist would demand these rules apply with precise pronunciation of stressed syllables. Most of us are not perfectionists. There were many enjoyable and hilarious offerings posted on the Limerick thread that did not follow strict meter. I find it is hard to write perfect meter. You can cheat a bit, but cheat too much and it won't sound right. To my ear, if you have the correct number of feet, you can get away with occasional fluffs on the beat. I also find that when I read a limerick I will automatically change the emphasis to make the beat correct. This is all relative of course, but if the rhythm is strong through most of the limerick, it can carry the reader over the rough spots.
Oh, the other thing about limericks? They are traditionally somewhat suggestive or outright bawdy. You can get away with simply funny, but a clean, serious limerick just doesn't fit the form.
There is a lot of controversy about the origin of limericks. The first known publication of a limerick collection was in 1820, although they were not then called by that name. Edward Lear later published his 'Book of Nonsense' containing limericks in 1846.
It wasn't until later that the word 'limerick' was used, and while there are theories as to why, very little supporting evidence exists. The first known use of the word ‘Limerick’ referring to a five-line verse was in a letter from Aubrey Beardsley, the artist, who used the term in 1896.
While the early collections were suitable for children, limericks took on a different character over the next several years, becoming naughtier. An amusing comment on this:
The limerick is furtive and mean;
You must keep her in close quarantine,
Or she sneaks to the slums
And promptly becomes
Disorderly, drunk and obscene.
Other features mentioned by some limerick sites as desirable:
A clever, unanticipated punch line as line five.
A Limerick that is not insipid or pointless.
Puns, word play, eccentric spelling, or some other witty feature.
"If not bawdy, limericks should still be rough in some way, such as through ludicrous use of language, ludicrous situation or ironic comment. Of course, if more than one of these can be combined, the limerick may be better."
And some caveats:
"Dextrous use of fancy words enhances a limerick, but clumsy use of fancy words does not help.
Bawdiness or salaciousness are not substitutes for cleverness.
This genre can and does take more ingenious rhymes than most other forms of poetry, but one should still strive to make the rhymes appear to be as natural as possible."
The information for this article came from these sites: http://www.umkc.edu/imc/limerick.htm
(For those who want to go further, this page of 'Limerick Taxonomy' had some interesting subtypes.)
My thanks to Nessime, Tay, and Elvenesse, who graciously permitted me to use their limericks.