No, really. I'm almost too embarrassed to post this.
All my life, I thought that people using "till" instead of "until" were doing so incorrectly. A simple dictionary check shows that they are, in fact, equivalent, although "until" is preferred at the beginning of a sentence.
In fact, it appears that "till" was the original, and that "until" didn't come around till later. Wow, that's going to be so weird to use "till" like that. I think I may avoid it, since it just seems so weird to me. The big challenge will be to not cringe when I see it in other people's writing.
What is particularly embarrassing is that I've done things like change that usage in things that I have edited. Not that I made it incorrect, but it was fine as it is.
How could I, as a person who considers himself more knowledgeable than average about grammar, who had good instruction in English, not have known this before now? It boggles my mind. I mean, really. Where did I get this misperception from? Did I just come up with it out of my own imagination? Was it mistakenly transmitted to me by someone else a long time ago? Is this a common misperception? Am I really just not that sharp? This is a major ego blow. I'm kind of dazed. Yes, it probably seems slly, for such a small thing. But, I mean, wow.