Before the ends begin, an explanation:
What kindled this posterial exploration?
Two men, like flint to steel, raised the spark:
Meriwether Lewis and William Clark—
Captains of an expedition to the West, 
with courage, luck, and flintlock rifles blest.
A third soul fanned the flame: Pierre Cruzatte
one-eyed chief boatman of the trek, he brought 
a myriad of skills crucial to the corps,
and plied the violin ’long with the oar,
his mast’ry adding more than just a tittle. 
He manned the bow and bowed a blazing fiddle.
For Captain Lewis, though, the epic tour
well-nigh concluded six weeks premature.
While racing down the mighty Missouri
he spied some elk, so landed in a hurry.
Cruzatte and Lewis split to track the game.
What happened next fore’er charred P.C.’s name,
while setting M.L.’s rump and wrath aflame.
Half-blind Pierre glimpsed movement. He took aim
and fired. The ball struck Lewis near the thigh,
wherewith the willows echoed with the cry,
“Damn you, Cruzatte, you myopic mother....”
The lead had pierced one cheek and then the other, 
causing pain and pique the Cap’n ne’er forgot.
Six weeks later, still nursing his sore butt,
The river bore him back to St. Louis. 
Cheering throngs lined the banks, amazed to see
The Corps alive, despite hunger and disease;
despite grizzly bears and prickly pears and fleas.
Yet Captain Lewis ne’er forgave Pierre
For that assault upon his derrière.
So I wrote a play about Monsieur Cruzatte:
fiddler, boatman, infamously bad shot.
I needed, though, the ideal word to use
for the Cap’ns booty, one that would amuse
a four-, eight- or ten-year-old, and still mean
“ass,” but that mom or dad wouldn’t find obscene,
a keister synonym all might abide.
In the end, I settled on “backside.”
But what of all the other buns and booties,
the haunches, hams, hindquarters and patooties?
I would have felt lexically disgraced
to have let all those waggers go to waste.
And thus the present volume came to pass,
a way to use my bottom words en masse—
sweet issue of a wounded captain’s ass.
Before you go a-hunting with a friend,
count working eyes. Just one? I recommend
staying home else you might get it in the end.