I subscribe to an electronic newsletter that each month sends out Linguistics-related news to readers in Denmark (and presumbly other parts of Scandinavia as well, where reading Danish is to varying degrees accessible for adults). One of the items from today was a blog written by the company BRO Communication. It concerned mixed metaphors and muddled proverbs, with examples in Danish formed in various ways, including examples which took two originally separate proverbs and crafted a third one out of a combination of the two, with less than fortunate results, of the kind that children and language learners can easily make. For example, there's a proverb in Danish "Jeg er ikke født i går", which fully corresponds to English's "I wasn't born yesterday". There's also a proverb with a similar proverbial meaning which reads "Han er ikke tabt bag en vogn", which is literally "he wasn't dropped behind a vehicle/wagon/car". (This last one does not however correspond to "falling off the back of a truck" in the proverbial sense in English). The combination of the two comes out as "Jeg er ikke født bag en vogn", which you could translate/transform into English "I wasn't born behind a truck (or some other vehicle)", which is equally difficult to interpret in either language, because it isn't an established idiom. Yet.
All this reminded me of experiences of learning a foreign language and working to get the idioms right. Proverbs are one of the later things to fall into place, and for second language learners it becomes a quite conscious memorization process, so much so that at times you can remember the context where you first heard the relevant metaphor or proverb (and who explained it to you).
Being a sociolinguist (Google 'sociolinguistics' if you're curious), and therefore a committed empiricist, I am wary of the blog's claims to report actual usages. Show me it in the original source or it never happened. And then, if we had the sources in speech or writing, we would be able to look at the context: was the new form made by a child of ten struggling to write for a teacher? A second-language learner in conversation with a public servant? And how was it received? Was it crossed out by an angry red pen? Was it negotiated through by the people talking together, so that the meaning the speaker was aiming for was achieved anyway, by a few twists and turns, a few resourceful moves? I wonder.