we also have to understand that during the time period Frank chose to adopt his "Costello" moniker, the Irish ruled the roost. Not only in the "underworld" but also the so-called legit "upper world" which Frank wanted to infiltrate...which he eventually seamlessly did with panache and to great success.
Think Vincenzo Plumeri, aka; Jimmy Doyle; Paolo Vaccarelli, aka; Paul Kelly, Thomas Eboli, aka; Tommy Ryan, etc.,etc.
This also applied to professional boxing:
In the early years of the last century, Irish were the "underdogs," so a lot of Eastern and Central European fighters with names that ended in "cz" or "ski" went into the ring calling themselves "Battling Ryan" or "KId Murphy," etc. In the Thirties, Jews were the underdogs, so some fighters built their public persona around being "Jewish."
Case in point: Max Baer, a German Catholic, always wore trunks with a Jewish Star embroidered on them. Ray Arcel, the legendary trainer, once said, "I seen that guy in the shower--believe me, he ain't no Jew."
