"Deuce and a half" for body weight
Solution 1:
The expression is from military slang for a large truck — that weighs two (a deuce) and a half tons.
I hadn't come across this expression before, but I have to say it doesn't seem very apposite to me. My car weighs nearly 2 tons, so a 2.5-ton truck doesn't sound particularly big to me. Wikipedia agrees, saying there are 8 truck categories — the lightest of which is for anything under 3 tons.
Anyway, it's not exactly "common", but here are a few dozen instances of "she's a deuce and a half" showing that it's far from unknown (even if the scale factor is a bit off).
Per comments below — unquestionably "a deuce and a half" is military slang, but it refers to the load-carrying capacity of the truck, not total weight. And Urban Dictionary's 2.5 x 100lbs = 250lbs is, well, an urban legend sort of rationalisation.
Solution 2:
In this context "deuce and a half" has nothing to do with the military truck. It is instead slang for a large person in the neighborhood of 250 pounds. Urban Dictionary defines the term as "a woman that weighs in the neighborhood of 250 pounds." Men also can be described as such, including news about the football player for which "recent internet rumors had... pushing the deuce-and-a-half mark (a.k.a. 250 pounds)." Yahoo answers also features a reply about "cool army nicknames" in which a fellow notes that his was deuce and a half because "I'm a big guy over 6 feet and while I was in the army I was about 250 pounds ex-football type."
On a related note, "deuce and a quarter" is the nickname for the Buick Electra 225 automobile, which was produced from the 1950s-80s.
Solution 3:
The term deuce and a half is for certain, slang for the military truck. And if you do a Google search, you will see it is not some light weight truck – it's BIG.
So, when used in the reference of a person's weight you can be sure it's not a term of endearment. As posted above, it could represent 250 pounds (200 for deuce and 50 for the half) – still it is not a term of endearment.
(Just a warning: if you say this to a woman, duck, because you are about to be punched).
Solution 4:
If you ever Googled the term you would definitely see the 2-and-a-half-ton army truck is the first thing that pops up.
Some people say it is the number axles or the axle load in addition to vehicle weight.
Never heard of calling a woman a duce and a half, however "deuce" is a term meaning "2" . It comes from the French "deux" probalby through tennis.
I would say definitely say it is American slang either about weight 250 pounds not Kilograms (551#) needless to say it is derogatory. I would even go as far to say it is more sexually based; referring the female anatomy either to cleavage or the rear end meaning a pair and a half, meaning of course very well endowed.
“Deuce and a half" is an extremely common term, and has been used, I would say, since there were motorized vehicles and trucks.
Yes, it is the term used for the LOAD capacity 2.5 tons (5000 pounds), and note, back in those days there were not many paved roads. So on-road was what today is called "off road"
Most common was in the early 1900's and especially after WWI (World War I) when all the surplus army trucks were put into service delivering goods on non-paved roads across the nation and world.
Remember also Mass and Weight are not the same thing.