Symbolism, Imagery, Allegory
You might be wondering how an Austrian from the 19th century wound up being so important to An Abundance of Katherines. For starters, Colin and Hassan visit his grave, which is really the grave of Fred N. Dinzanfar, Lindsey's great-grandpa. Now there's a cool anagram if we've ever seen one:
Fred N. Dinzanfar = Franz Ferdinand
But the Archduke is more important than just having an anagrammatic connection to Lindsey's family: he's famous for being shot, so he didn't really do anything to get famous. While Colin's off desperately trying to matter, Ferdinand matters to the world for doing nothing.
He's not really in the novel, but important to it because he's talked about so much. This historical guy becomes a symbol of what happens in life: while some people are remembered, others are forgotten, and a lot of times it doesn't matter whether we try to do something noteworthy or not. History gets to decide, ultimately, whether we're remembered.