"Used to" isn't actually a weird metaphorical thing.
To "use" can mean (though in most contexts this meaning is obsolete) to do something regularly or habitually. So "I use to do X" means "I am in the habit of doing X", and "I used to do X" means "I was in the habit of doing X". The implication that you don't do it any more is a Gricean thing -- if you were still doing it you'd say "I use to do X" rather than "I used to do X".
Nowadays no one uses "use to" in the present tense and no one is thinking of the above when they use "used to" in the past tense. But that's where it comes from.
[EDITED to add:] I see that this has got some downvotes, but I'm having trouble figuring out why. If you read this and didn't like it, I'd be very grateful if you let me know what problem(s) you see. Thanks!
(Of course maybe it's just random drive-by haters, but more likely there's something it would be useful for me to know. Maybe something I wrote is wrong, in which case I want to know. Maybe to some readers it looks like I'm insulting the person I was replying to or something, which wasn't at all my intention and if that's going on then I should probably clarify or apologize or something. I dunno.)
This is actually my favorite kind of HN discussion. I think the added context is really interesting, despite maybe being a bit of a tangent. English is full of "orphaned" words and phrases that no longer make sense in general usage (no one ever refers to a "gamut" unless something is "running" it). I had no idea that "used to" was an example of this.
I think maybe the tone of your comment has a bit of "well actually" that bothers some people. It's the difference between sharing a fun fact versus policing correctness. The interesting point is that "used to" is weird, but not for the reason that the parent comment assumed. That's a genuinely fun fact that I enjoyed learning.
Yeah, I think the (entirely unintended, as it happens) well-actually-ness probably rubbed some people the wrong way. Ah well, I'll hopefully do better next time.
> I see that this has got some downvotes, but I'm having trouble figuring out why. If you read this and didn't like it, I'd be very grateful if you let me know what problem(s) you see. Thanks!
Sure thing, I'll try. Your comment does not contribute to the discussion. It appears that you completely missed the point the comment you replied to made. The point was that “used to” has no inherent meaning and would seem odd to someone who is very new to English, and your response was just to explain what it means. You argue that it's not actually that odd but then basically prove how odd it is by highlighting how much obscure/obsolete knowledge is required to fully explain it.
Huh, interesting. For what it's worth[1], here's how I see the same matters:
[1] Which may not be much; I will in no way be offended if you don't care.
I didn't miss that the person I was replying to said that "used to" is odd and confusing. I wasn't arguing that "used to" isn't odd (still less that it isn't confusing for novice English-speakers -- it certainly is).
I was arguing that it's a different kind of odd from e.g. "at trække vejret" in Danish, and (to me, but evidently not to you!) I think it's an interestingly different kind of odd, which is why I thought it was worth pointing out.
I wasn't attempting to "explain what it means", which obviously the person I was replying to already knows. I was attempting to explain why it means what it does.
(In particular, it isn't true that "used to" has no inherent meaning[2]. It really is a past tense of "use", and while the specific meaning it's a past tense of is largely dead you can still, if you squint at it, see how it's of a piece with the other meanings of "use".)
[2] Except in so far as no word has inherent meaning.
Evidently, none of that came across the way I intended (or, perhaps, it came across fine but I misjudged how interested anyone else might be in the history): I should probably either have been more explicit or not bothered at all :-).
Now you missed my point as well. I didn't say it wasn't interesting, and I didn't say anything you said was wrong on a factual level. I said, “Your comment does not contribute to the discussion.” Interesting or not, it's just off topic and out of place, and that's why it comes across as you missing the point.