I’ve been mildly curious about this one for decades, but I was never sure I wanted to know the answer. Finally, curiosity has overcome.
In the song Aqualung by Jethro Tull, the lyrics say, “Leg hurting bad as he bends to pick a dog-end…” How, exactly, does one pick a dog-end. And which end? And why would it make your leg hurt? Yuck.
And in Born On The Bayou by Creedence Clearwater Revival, they say “I can still hear my old hound dog barking, chasing down a hoodoo there.” What’s a hoodoo?
dog end “The end of an already used cigarette.”
A dog end is a cigarette butt, so if you’re picking them up you’re really desperate. A sore leg is just the icing on the cake.
Merriam-Webster’s Collegiate Dictionary, 11th ed. (pasted with no attempt to fix goofy characters):
Main Entry:1hoo£doo
Pronunciation:h-()d
Function:noun
Inflected Form: plural hoodoos
Etymology: perhaps alteration of voodoo
Date:1875
1 : a body of practices of sympathetic magic traditional especially among blacks in the southern United States
2 : a natural column of rock in western North America often in fantastic form
3 : something that brings bad luck
4 : NONSENSE, HOKUM
–hoo£doo£ism -i-zm\ noun
A dogend is simply a cigarette butt long enough to still provide a few puffs.
I always guessed the pain in the leg was simply arthritis or stiff joints from sleeping on the ground, although there may be more to it.
I always figured the hoodoo was just a spook–not a genuine ghost, but the sort of phantom prey that dogs are likely to pursue for fun.
Yeah, I looked that up, too. None of those sound like something a boy would remember his hound dog chasing down.
NB: “Chase down,” unlike “chase” carries an implication that the thing being chased was caught, and that it was actively running away.
At least JT didn’t use the synonymous Britishism “fag end”.
A hoodoo is a ghost, a haint, a mysterious something out in the swamp. Don’t overthink the “chasing down” part. I think Fogerty was from California, not Louisiana.
I see your point about the distinction between “chase” and “chase down,” but I think it’s still OK in this sense. The dog intends to catch it, even if he never will because it’s just a figment of his imagination. Our dogs are always barking their fool heads off over nothing at all.
Besides, it’s just a song, dude. 
I cringe every time I hear Billy Joel sing “And your momentos will turn to dust . . .” but I still like the song.
I don’t get what’s supposed to wrong with this.
A memento is a keepsake or souvenir, not a thought or abstract. Keeping them until they turn to dust makes perfect sense.
Your cited definition of hoodo is also lacking. Dictionary.com has several definitions that would work better in context.
A hoodoo, therefore, is something that can be chased down.