So, has anyone else heard this term? I’ve known a few folks who did this job, and they referred to these tanker trucks as honey wagons. None of them knew why.
Anyone?
(Of course, I had some reasonable guess, which I will omit for now, lest I be making this a ‘vote for the best guess thread’ and mihgt see me question shipped over to IMHO)
My completely uninformed guess is that flies are attracted to them, as to honey.
In all the events in which I’ve participated that used chemical toilets (and that’s quite a few), I’ve never heard this term.
On the AIDS Rides (where the campsites call for dozens of them), we call them sucker trucks. I trust I don’t need to explain that one.
I thought it was used to make fun of the stench. The odor is said to be “as sweet as honey”, obviously ironically.
Because no-one wanted to drive the “shit tanker”?
I can’t give you the etymology, but I spoke to some elderly people at a history society in Oxfordshire, England, and they said that in the days before the villages thereabouts had drainage or septic tanks, there was a guy who came round with a horse and cart every day to pick up each house’s “honey bucket”, and it too was called the “honey wagon”. This would have been in the 1920s.
I’m guessing it’s just a jokey euphemism.
A WAG, of course, but I think it may have something to do with the old colloquialism for open sewage canals (generally in poor rural areas), “Honey Ditch” or “Sugar Ditch”.
What else can you think of that is ok to say in public, and is also yellow and chunky?
An old Polish-American guy once told me that in Poland, the guy who came to clean out the cesspool was called a “honey dipper.”
I almost typed “honey dripper,” which is a whole different story.
The ones I used up on the slope were called honey pots.
Dark brown humor if’n you ask me.
There is no need to go to Poland to find the term honey dipper 
“Honey Bucket” is a particular brand of port-a-potty that I’ve seen. Perhaps “Honey Wagon” is the brand name of that company’s port-a-potty-emptier truck?
They were called honeydew wagons when I lived in Japan in the 1950s.
The color of urine is yellowish, a bit like honey.
When I was on a gold mine tour in Apache Junction, AZ, they told us that some unscrupulous miners would occasionally hide a nugget in the loo and then try to fish them out…and said folks were knows as “honey dippers”.
The term is cited first in print in English in 1923. The cite suggests that the term was actually understood more by Europeans than Americans. A 1930 cite suggest it was a “French manure cart.”