As has been mentioned in the introductory post, classic Language Log article #4 is now a 404 page. I have no idea whether it had ever been anything else (I suppose I could check Wayback Machine, but I’m not sure it would work; most likely, it had been yet another test entry of some kind, and had been deleted within a few days of being posted).
So instead, I’m devoting this post to Piotr Gąsiorowski’s magnificent etymology of the Indo-European word for the number “four”.
To summarize, the theory is that the Proto-Indo-European root for “four” (which is otherwise unusually long for PIE) is morphologically derived from a root meaning “pair”; I’m not sufficiently familiar with PIE morphology to reasonably consider or dispute the specific details, but from a Russian-based perspective, he is saying that четыре “four” is related to чета “pair” and чётный “even” (something mentioned as a possibility in several Russian etymological dictionaries – but without actual details).
Most of the etymological dictonaries available online link the latter two words to South Slavic words meaning “troop, crowd”, then to считать “count” (compare чётки “prayer beads”, which does appear to derive from считать), then to читать “read”, and perhaps even farther on. Russian Wiktionary, in particular, doesn’t even try to decipher the mess, and gives several dozen assorted words (including all of the above except четыре “four”) in the “related words” tab.
However, one word that does – at least as far as I can tell – appear to derive from the root for “pair” as Gąsiorowski sees it (but does not appear to be mentioned in his posts on the topic) is сочетание “combination”. (And сочетать “(transitive) to combine”, and сочетаться “(intransitive) to combine, to fit, to marry”, which are trivially related to it.)
[Though the word *четать “to form pairs”, listed by Gąsiorowski as supposedly Russian, might be a confused reference to some version of the above; it is not otherwise a word I recognize.]
To be honest, I thought that it is a transparent calque from Latin combinatio (or, perhaps, from Greek syndyasmos). However, apparently there is a Bulgarian word съчетавам “to combine” (indeed, apparently, the Bulgarian for “combination” is съчетание), which is clearly related, but South Slavic.
This means that either it derives from the South Slavic root meaning “troop” – which doesn’t seem likely, given the Latin and Greek development, which is at worst parallel – or the root meaning “pair” had at some point existed in South Slavic (in which case the respective word might well have been, in fact, a calque – perhaps at the Old Church Slavonic stage).
I’m actually surprised that this word is not mentioned by Gąsiorowski (at least, not anywhere that I could find); there are otherwise no South Slavic cognates, which makes it easier to introduce spurious ones. (Though this doesn’t help Vasmer, whose entry for чета mentions both.)
In any case, even if it is unfalsifiable (or perhaps even unverifiable) at this point – great etymology.
(Yes, the link to Gąsiorowski’s blog was on purpose. I fully intend Gąsiorowski, or indeed his commenters, to see this post; even if they just end up picking out my linguistic mistakes. I’m hardly an expert; I’m just a random linguistically interested guy.)
(Also, sorry for such an extended digression. But I wanted an article #4 in the Language Log Twelve Years Later series, I really wanted to comment on this etymology, and there wasn’t really anything worthy of commenting on at the actual Language Log #4 page anyway.)