I used to go to Brighton

I understand what 'used to' means

What is the origin of the 'used to" as in "I used to go to Brighton".

I understand what it means but why 'used to'

Solution 1:

It's a good question, and I think I can answer it best this way:

All aspects of human communication tends to get simplified wherever possible and as soon as possible, and ever-more rapidly; we want to get the message across as concisely (is) as possible, and so we leave out the more complex syntax, bigger words, words altogether, abbreviate, et cetera (etc).

Just as HAVE TO / HAD TO means something along the lines of, "It is/was a must and the expected thing to do", USED TO means something like "I was in the habit of doing it and I'm no longer (for one reason or other) in that situation (or predicament)".

(Note the 'and' in both phrasing above and see below*)

And so instead of the more long-winded, "I was for a significant period (in my current lifetime) in the habit of going to Brighton on a regular basis, and am no longer there,..." we just say "I used to go Brighton".

USED TO (semi-modal) ("use+d" means just that 'usage' + past. 'to' means 'for the purpose of') Like all modal and semi-modal verbs, they serve to indicate modality, and so they may also vary in meaning according to mood, by the way.

*The so-called 'phrasal verbs' tend to serve the same purpose, and often they are used to condense two actions into one. So, "I get up" means I awaken and leave the bed. "The plane has taken off" means that it started its trajectory and NOW (has) lifted off the runway, where "has" btw means nothing more than 'the current situation linked to a past event'.