Not sure if anyone has studied this, but, two related questions that seem interesting to me:
(1) What English word with more than one acceptable spelling has two spellings that are used closest to 50/50… ie, it’s very hard to point at one as the more common or more correct one?
(2) What two English synonyms are the most nearly identical in meaning? I guess there are two forms of this:
(2a) Two words which have the closest-to-identical meaning when used in a normal sentence (so “big” and “large” fits pretty well, although I think “large” has more of an implication that this is referring to actual physical size)
(2b) Two words which can most commonly be swapped for each other (so two words wouldn’t qualify for 2b if one of them was in a lot of idiomatic expressions or phrases…)
(Not sure if this is the right forum, but this is the kind of thing that someone might randomly have run a million words of English text through some filter to get the answer to…)