(It turns out that both vagueries and vagaries are real words, with similar meanings, so that both, or either, are appropriate for the title of this thread!)
It's amazing that sometimes the most peculiar spelling or pronunciation conventions can be so entrenched that I don't even notice them.
I only recently noticed how strange is the verb prove.
A scientist must prove her theory, a prosecuting counsel must prove the guilt of the defendant, bread dough is left to prove overnight.
In British English it's pronounced so that the o sounds like the oo in food. It gets odder: the past participle is not proved, it's proven - and this time the o sounds normally, like owe.
"Case not proven!" barked the judge. The theory of Evolution has still not been proven after a hundred years of acceptance.
And there's a noun form the word, too, which is proof. And suddenly we have two o's so that the oo sound makes sense, but now the v has changed to an f. Language never ceases to fascinate.