There is a new phrasal verb “be a thing” which lets us conveniently talk about such constructions. That is, “now and then” is a thing—an idiom, with a specific meaning outside the wording—but “then and now” is not a thing.
You will note that all of the semantic constraints they propose place the item with a “positive” aspect first—I wrote a blog post about this[1].
There is also a related notion of “stormy petrel”[2] which I wrote a poem about[3] back when I had lots of hair.
As a side note, "then and now" is actually a common phrase used to describe comparisons of old and recent depictions of the same subject, e.g. photographs of celebrities.
"Whorfer" = adherent of the Sapir-Whorf hypothesis, which (very roughly) says that language structure and vocabulary influences or determines what thoughts can be thought. e.g. if your language does not have a word for "yellow", do you classify colors the same way as someone who speaks a language that does?
You will note that all of the semantic constraints they propose place the item with a “positive” aspect first—I wrote a blog post about this[1].
There is also a related notion of “stormy petrel”[2] which I wrote a poem about[3] back when I had lots of hair.
[1]: http://evincarofautumn.blogspot.com/2014/08/adjective-valenc...
[2]: http://www.kith.org/logos/words/lower/petrels.html
[3]: https://www.youtube.com/watch?v=fRlpRFs2L30