These cryptic vowels began popping up on Austrian public buildings during the reign of Frederick III (1440-1493). Frederick never explained why he chose this monogram, which has led to conspiracy theories worthy of Dan Brown.

Scholars have suggested:

Austria est imperio optime unita (“Austria is the empire best united”).

(“Austria is the empire best united”). Austria erit in orbe ultima (“Austria will be the last (surviving) in the world”).

(“Austria will be the last (surviving) in the world”). Austriae est imperare orbi universo (“It is Austria’s destiny to rule the whole world”).

Of course, he may have been using his native tongue – Alles Erdreich ist Österreich untertan (“All the earth is subject to Austria”).

Frederick died without ever revealing the secret.

James Joyce Bonus: Speaking of mysteries, you’ll find the same initials in Chapter 9 of Ulysses:

“I that sinned and prayed and fasted.

A child Conmee saved from pandies.

I, I and I. I.

A.E.I.O.U.

–Do you mean to fly in the face of the tradition of three centuries? John Eglinton’s carping voice asked. Her ghost at least has been laid for ever. She died, for literature at least, before she was born.”

Joyce lived and taught in Trieste (Italy) and Pola (Croatia) – both cities in the Austro-Hungarian Empire.