Why is St. Erasmus St. Elmo in Italian?

New blog on the kid: Why Did Tolkien Love Trees? · Φιλολoγικά/Philologica: Why is St. Erasmus St. Elmo in Italian?

First, I'm going out on a limb on citing a name from memory.

Heremod seems to have been on some point pronounced Herismod. I may be wrong, and I couldn't find it. Or even simpler, Erasmo was at some point pronounced Eramo, close enough to Heremod without an -s- inside. Because Italian tended to lose -s after vowel. Late Latin on a colloquial level had two cases, and for masculines of the second declinsion, the nominative singular and accusative plural both ended in -os (variously spelled -os or -us), while the accusative singular was -o and the nominative plural -i. Italian kept the two forms without an s, so, Erasmos could have been pronounces Eramo at some point.

Here is where Heremod comes in. It sometimes shortens to Hermod (in Norse myth the herald of the gods, probably after Hermes), and that sounds well within the reach of Ermo, one of the Italian versions of Erasmus.

And the other one? Helmut has an L were Hermod has an R, and so Helmut would be pronounced Elmo, precisely as Hermod would have been pronounced Ermo.

Since Helmut first was a given name, but since the 1500's also exists as a surname, we can take it Helmut is Medieval. Old enough, perhaps, to explain Elmo.

And, at least in the combination "fuoco di Sant'Elmo" the phrase is noted from the 1560's so presumably after the earlist mentions of Helmut./HGL