"Ironic" was being used to mean "coincidental" at least as far back as the 1960's, by DC Comics. They would introduce these rather pointless coincidences (like the many people who know Superman whose initials are L.L.), and would frequently comment in the yellow border of the panel that what's going on here is ironic. It wasn't, but perhaps that's how a generation of comic book readers came to think this was correct usage. Abusive comment hidden. (Show it anyway.)
"The gun that Lee Harvey Oswald [wiki] allegedly used to assassinate President John F. Kennedy..."
Good grief. "Allegedly?" The commie shot JFK, get over it.