Every so often, I come across someone reacting with surprise and puzzlement at some word or idiom — because it’s unfamiliar to them (they don’t recall having heard it before), because it strikes them as rare, because they find it opaque, because it sounds peculiar, whatever. Often the object of surprise is a reasonably common and long-standing usage, so that the complaint is itself puzzling.
In this vein, Michael Thomas cried out on Facebook on Sunday:
what the hell kind of word is “RECENCY”?
Melinda Shore weighed in with the first response (“It’s an excellent word!”); Ken Callicott playfully ventured the answer “A noun?”; and Garabato Abrelatas Inalámbrico Arvejas thought to check a good dictionary:
Huh. OED dates it to 1620. I guess it’s pretty cromulent.
The other responses were all over the map. I’ll get to them eventually, but first a straightforward answer to Mike Thomas’s question.
The word recency: basics. Recency is one of two noun derivatives of the adjective recent; recentness is the other (I exclude the awkward alternative recentity ‘recency, newness’ (OED), which hasn’t been attested for 135 years and was rare even back then.) Recentness has the derivational suffix -ness, an all-purpose nominalizing suffix, while recency has the derivational suffix -cy, which is restricted to Latinate stems (compare accuracy, celibacy, delicacy, effeminacy, frequency, privacy, secrecy).
(This suffix -cy originates from an adjective-forming suffix -y — one of several in English — in combination with a stem-final t; /t/ is “softened” to /s/ before various specific suffixes.)
Recency ‘the state or quality of being recent’ — opposed to antiquity — is the older derivative noun. First cite 1620; OED3 has cites from fiction, from a variety of technical fields, and from expository prose, for instance:
 1943 G.-H. Smith et al. Japan 5 Although the best land is cleared, stumps remain in many places, testifying to the recency of settlement.
(Instead of the recency of settlement, how recent the settlement was or how recently the land was settled would be possible, but the recency of settlement is more compact.)
Recentness ‘the state or quality of being recent; recency’ (note that the OED glosses recentness via recency) came along a bit later, with a first cite from 1647. A recent cite:
 2004 Times Lit. Suppl. 17 Sept. 14/2 All of them, in Western European terms, have a recentness about them, literally so in the case of Norway and Finland which have yet to celebrate their centenaries as independent nation-states.
The word recency: advanced class. In general, -ness with Latinate stems is more recent than Latinate suffixes (like -cy and -ity) with such stems and is more transparent semantically. But sometimes the difference is subtle: I find recency in citation  above more satisfying than recentness would have been, but I’m not sure why; while in  I find recentness much more satisfying than recency would have been.
Another characteristic of words with the Latinate suffixes is that they are inclined to develop specialized uses. This is true for recency; see OED3’s subentry on recency as a technical term in psychology:
Psychol. The fact of being recent, as a factor in memory or apperception; spec. the fact of an item having been encountered more recently than other items, as increasing its likelihood of being remembered. Freq. attrib., esp. in recency effect. Cf. primacy n. 1b.
The first cite is from 1891. The most recent one:
2001 G. Ward in J. Andrade Working Memory in Perspective x. 221 The size of the memory span, but not the size of the recency effect, was affected by the age, intelligence,‥and language processing ability of the participants.
(Note the reference to primacy in the OED‘s gloss for recency. In presentations of material — including sentences — two items are especially salient: the first (primacy) and the last (recency).)
More recently, in a 2005 Language Log posting, I introduced the Recency Illusion (if you’ve noticed something only recently, you believe that it originated recently) and its frequent companion the Frequency Illusion (once you notice a phenomenon, you believe it happens a whole lot) — with the result that Charlie Fulton reported on Facebook:
I googled [recency], and Arnold was the second hit (link to Wikipedia entry)
(I don’t think that Recentness Illusion or Frequentness Illusion would have done as well as the labels I chose.)
What are other alternatives to recency and recentness? On Facebook, Max Vasilatos suggested the coinage recentishness, referring to something merely recentish, not necessarily actually recent (compare the somewhat more common coinage recentishly), and Rod Williams playfully offered lateliness, a nominalization of the adverb lately ‘of late, recently’. But this is just fooling around with vocabulary, if you decide you don’t want to use recency (or recentness).
The remaining already-established alternatives are, primarily, newness and, less satisfactorily, novelty, but these convey greater freshness than recency (or recentness) and are unsuitable in many contexts — compare recency in  with newness (though newness would work in  as an alternative to recentness).
(The most entertaining Facebook response came from Corry Wyngaarden, who played with geologists’ use of recent to refer to the Holocene epoch (or era), referring to roughly the last 10,000 years, and recommended the Bon Iver song “Holocene” (video here).)
Surprised responses to recency. We’re left with people who simply accepted Mike Thomas’s implicit questioning of recency as an English word (“what the hell kind of word”, implicating ‘not much of a word, not really a word’) and cast about for things that might be wrong with it.
Bill Halstead judged it to be an error, offering refudiate and misunderestimate as parallel examples.
Frank McQuarry (correctly) disagreed with that and suggested instead that
It’s business-speak. It’s the amount of time since some event –like a purchase — happened.
Here McQuarry is trying to contextualize the word from his personal experience with it, or at least the experience that comes first to mind when he thinks about the word. People do that a lot when they reflect consciously on word meanings and uses in social contexts, dredging up memories of these matters and generalizing from their first catches — usually quite inaccurately, even as an account of their own experiences. (I don’t doubt that recency is used in business contexts, but it is used in vastly more contexts than that.)
One step further with Chad Kelsey, who imagines sociocultural associations with the word:
Sounds like some word the ladies of the Real Housewives of NJ would use.
There are some assumptions there about the social world of the Real Housewives of New Jersey and about the way they use language, but I wouldn’t venture to try to unpack these.
Finally, there are associations with phonologically similar words, which might interfere with some people’s judgments of words. So we get Rod Williams playfully (again) connecting recency to regency (while combining this with the semantics of recency):
Recency sounds like a regency from not long ago…
Mike Thomas added to this that he kept seeing the Hyatt Recency too.
(I must admit that elegant sometimes unfortunately calls up elephant for me, but I’m not agin the word.)
Some of this discussion is merely entertainment, but some of it illustrates what happens when people reflect consciously on language use, an enterprise that can lead people far astray. Sadly, many who offer advice about language are no better than ordinary people at this task, but still they set themselves up as experts.