I recently ran across the extremely obscure word aprakos (so obscure it’s not in the OED); here’s what Wikipedia has to say:
Aprakos is a kind of Gospel or Acts of the Apostles book, otherwise known as weekly or service Gospel (Acts). In aprakoses, the text is organized not in the natural order of books, but along with the weekly church readings starting from the Holy (Easter) Week as used in the Eastern Orthodox Church. In particular, the text of Aprakos-Gospels begins with the first chapter of Gospel according to John (In the beginning was the Word…), whereas regular Gospels (Tetra-Gospels) begin with the Gospel according to Matthew (The book of the generation of Jesus Christ, the son of David…). Many of the oldest Slavic manuscripts are aprakoses, like Codex Assemanius or Ostromir Gospels.
It gives me a combination of heartburn and a warm, fuzzy feeling to see the phrases “Codex Assemanius” and “Ostromir Gospels” (grad school memories), but never mind that: what kind of word is it? It looks Greek, and if we go to Russian Wikipedia we find that it’s from Greek ἄπρακτος ‘not doing/acting, idle’; Vasmer tells us it’s from the phrase ἄπρακτοι ἡμέραι ‘idle days, holidays.’ All well and good, but where did the -t- go? This isn’t a popular word, where all sorts of things can happen in oral transmission, but a learned word that presumably got copied straight from Byzantine manuscripts into Slavic ones; did some copyist omit the tau and nobody noticed? If it had been borrowed normally as apraktos I might be tempted to complain about the plural in –es in Wikipedia, but since aprakos isn’t Greek, it would be silly to coin a pseudo-Greek plural aprakoi. I don’t know why I’m bothering you with this trivia, except that you’re presumably taking the week off like sensible people, and hardly a soul will be affronted by it.