I recently encountered the phrase "for choice" to mean "by preference". At first it didn't look like idiomatic English to me, but a web search turned it up in a few other places. Is this common in some dialect other than mine (in British English, perhaps)? And is it native to that dialect or borrowed from some other language?
As in "For choice, I'll eat coxes, but other kinds of apple will do", yes?
It is an odd phrase, but it's not unfamiliar to me (in the UK). It seems much less formal to me than "by choice", but synonymous with it.
I can't think of any particular origin for it, or reason for "for" rather than "by". But idioms often have idiosyncratic prepositions: consider another phrase which means much the same "to my mind". Why "to"?
I'm not quite sure what you are encountering. I can think up of two usages for "for choice".
"Canadians for choice", or "Republicans for choice", or "Feminists for choice."
In this case, "choice" is the noun, and its meaning is "the right, power, or opportunity to choose", and such "Canadians for choice" are slogans that emphasize their goal to promote the right for "Canadians"(in this case) to choose as they like.
Another instance of usage of "for choice" is in the idiom "spoilt for choice", which means:
Having such a selection of good choices, that deciding which one to pick is difficult.
Example sentences could be:
I was spoilt for choice.
Adam was a complete supporter for choice
It's not an idiom, so there's no origin.