Shouldn't we accept that words change in meaning over time?

True, words like "cool" and "gay" gained new meaning via a process of modern association with their understood meanings, but BTQ abuse rises from a misunderstanding of its original use. It would be as though people started using "the die is cast" to mean dying, simply because the word "die" is in there, without any knowledge of Caesar. Is there any idiom -- not a single word, but a full phrase -- whose meaning has changed over the years, simply by virtue of its being misunderstood by the linguistically inept or the historically ignorant?