“Fixing one’s wagon” seems like a right neighborly thing to do, assuming your neighbor has a wagon that needs fixing. How did this morph into meting someone his comeuppance?
. . . My WAG is that “fix” is used in the sense of immobilizing something.
The Oxford English Dictionary defines “to fix (someone’s) wagon” as:
And defines sense 14(c) of “fix” as:
Fun fact: the first known author to use “fix (one’s) wagon” in print was Truman Capote, in Grass Harp (1951):
Now if you have a wagon, and I have a wagon, and I have a crowbar…
I might fix your election too.
My wagon is ship shape and Bristol fashion, but as long as you’re offering… I could use some help down at the mill. You see, something has out askew on the treadle.
Wait, **SiXSwordS **- what’s the matter with the mill?
Martin Abzug(Bella’s husband), Spearhead 1946.
“I’ll fix your wagon for talking back.”
… We’ll go down to the crawdad hole …
I think he posted that somebody shouted at a school full of tribbles.
Sum’in gon owt 'skew on’t treadle
I bet you didn’t expect the Doper Inquisition.
After you fix my wagon are you going to clean my clock?
First he has to settle my hash.
Don’t mock my smock or I’ll clean your clock.
Take ya to the feckin’ cleaners, he will.
If you’re going to fix my wagon, I’d appreciate it if you paint it as well.
Don’t leave in a huff - I’ll call you a cab.
OK, you’re a cab.
Nasty Canasta fixes Daffy Duck’s little red wagon. (A trifle loud.)
I’ll clean your clock was one of my father’s favorite threats; he would also threaten to clean someone’s plow.