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

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. [1]: http://evincarofautumn.blogspot.com/2014/08/adjective-valence-and-linguistic.html http://evincarofautumn.blogspot.com/2014/08/adjective-valenc... [2]: http://www.kith.org/logos/words/lower/petrels.html http://www.kith.org/logos/words/lower/petrels.html [3]: https://www.youtube.com/watch?v=fRlpRFs2L30 https://www.youtube.com/watch?v=fRlpRFs2L30