MetaFilter user lapsangsouchong posted an interesting AskMetaFilter question: “Which of the thousands of neologisms coined in the Turkish language reforms of the 1920s and 30s stuck, which ones didn’t—and why?” In the course of the discussion he posted this fascinating anecdote:
The word günaydın, ‘good morning’ or ‘good day’, was coined at this time and achieved widespread currency. But it was one of a pair, with tünaydın, ‘good afternoon’. This has achieved absolutely no currency except in schools. In the morning, when the teacher comes into class, the children stand up, the teacher says “Günaydın!” to them, and they say the same thing back; and in the afternoon, when the class comes back after lunch, the same ritual is repeated but with the word “Tünaydın!” Outside this context the word is never used. The explanation my friend suggested is that while gün was and is the normal word for day, so the new coinage (which literally means something like ‘bright day!’) made sense, tün was one of the ‘new old’ coinages, an ‘authentic’ ancient Turkish word… which no-one ever used. So a new word formed from tün had less chance of sticking than a new word formed from gün, despite 65 years* of teachers saying it to their classes every day after lunch.
*According to Nişanyan it was coined by the TDK in 1945. Bizarrely, Nişanyan has tünaydın but not—except in the entry for tünaydın—günaydın.