After I read Grace (for what turned out to be the 3rd total time) the chapter about Malaria from Little House on the Prarie, she was all aflutter about the different theories presented in the chapter. Mrs. Scott thought the fever was about the watermelons she said, and Ma thought it was about the night air, she added, but they didn't know that it was because of the mosquitos.
The reason Grace found the chapter so interesting was that it ends with a little coda that says "they didn't know that..." and then explains how mosquito bites carry malaria. That simple phrase -- "they didn't know" -- was quite captivating and led to another homily from Grace about the limits of human knowledge (sometimes little boys and girls don't know... and sometimes mommies don't know... and sometimes daddies don't know... and sometimes teenagers don't know...).
What I found interesting was her use of about. Particularly, it struck me because in teaching Spanish to English speakers, the pronouns "because" and "about" (both of which often translate as the same word, "por") stick out.
Grace's use of "about" seems in line with Spanish "por" which can mean anything from "by way of" to "by cause of" to "by means of." What's odd, though, is that none of these uses of "por" translate to "about." In fact, the only clear case where "about" translates to "por" is the spatiotemporal sense ("it's about five" or the somewhat antequated "somewhere about").
The most common use of "about" I can think of is the meaning that "it has to do with" or "its topic is." I suppose this makes sense... "Mrs. Scott thought the fever had to do with watermelon but it was because of mosquitos."
Still, it all gets me thinking about our friends the prepositions, all of which have multiple meanings applying across multiple domains (causality, space, time). It seems totally natural even at a much younger age to expand meanings (Clara's language constantly demonstrates this). What is trickier is how the meanings get cut off, so that we learn to say "she thought the movie was about pandas" but "she thought the fever was from watermelons."