For example in the idioms "left and right", "left, right and centre", and in many contexts where both left and right are mentioned, it seems that the left usually comes before the right. Why is this so?
I guess the begged, or zero-th, question: is there a preference when ordering left and right? Some people use "right and left" as well.
I'm not sure how useful an Ngram search would be, due to both left and right having multiple meanings, e.g. "she turned to her right and left the house" or "he stood up, left and right then …".
Best Answer
As one answer to the question behind "left" vs "right"
-- i.e, why do fixed phrases get frozen in one form, like tide-locked moons? --
there is one interesting and probably correct theory, advanced decades ago in a paper by Cooper and Ross entitled 'World Order', which is worth reading, if you're interested in the phenomenon.
It compares frozen meaningful doublets ("freezes"), like ladies and gentlemen or Scotch and soda,
-- but not the other way round) with meaningless doublets like hocus-pocus or dribs and drabs
-- but not the other way round) and finds that they follow the same phonological rules,
which are common in many languages.
In addition, there is a consistent set of semantic rules for which part of a freeze comes first.