I'm not saying it's faulty or wrong. I really meant what I said--where does it come from?

English, as taught in non-English-speaking countries to non-English-speakers, actually seems to be a somewhat different subject, with its own terminology, than in English-speaking countries. (That's reasonable, because to us, "English" is just a refinement of things we already know). For example, I'd never heard the phrase "phrasal verb" before I started using italki. Thinking I might just be out-of-date, I've asked fellow U.S.-native-speakers "have you ever heard of a 'phrasal verb?' Do they teach that in school nowadays?" and nobody has heard the term. Finally I had a chance to ask a high-school English teacher, and she said "phrasal verb? I've never heard that term, what does it mean?"

I can only confirm that "sth" was used by my English teachers, and thus also by us students, when we learned English in high school. In French we used qc for "quelque chose", which also means "something". I don't see it as an 'official' abbreviation; we only ever used it in vocabulary lists to remember connections such as "hand sth to so" (so being someone). We would never have used it in a test. Perhaps someone will know more about where it comes from, but I never saw it as a problem. It's simply an abbreviation for a very frequently used word where spelling it out wasn't necessary.