If it's 3 non-repeating unordered words, the minimum vocabulary will need to be 256*3 = 768. Realistically you'll need an order of magnitude larger. That's a pretty large vocabulary.
You need 256 base words, and two substitute words, one of which substitutes for the first repeat, and the other for the second, so 258 words total.
Okay but that's a strange requirement. A 'big burger house' isn't a 'big house burger', after all.
I had read 'unordered' as 'the collation order of the words has no connection to the ordinal rank of the underlying byte', for some reason
To some degree I agree, but there are also a lot of cases where different orders aren't distinguishable easily. "Light bright red" and "bright light red" is the best I can come up with quickly but I'm sure you get the idea.