According to a recent article from wired magazine (in italian) Hai un’idea geniale? Fai come Mr Arduino, regalala. E diventa ricco - Wired.it
The board was named after a pub in the surroundings of the Interaction Design Institute, Ivrea , Tourin , Italy.
Obviously Arduino is not just a pub's name, it's a proper (not so common) noun!
Arduino is still used as a name and surname, in Italy and probably in most european countries. Infact according to a great italian site for name and surnames (in italian) http://www.gens.labo.net/it/nomi/genera.html?nome=arduino :
"It comes from the germanic name, Harduwin or Hardwin, made by hardu-, "strong" and wini, "friend", spread by the tribal population of the Franks in the IXth century, consolidated thanks to the prestige of few saints and the Italian king Arduino d'Ivrea (1002-1015).
The name day can be celebrated the 15th of august in memory of Saint Arduino from Rimini, died in 1009."
As of today this noun has more spread use as a surname
As you can see from the graph here ARDUINO significato origine cognome famiglia | Gens
The name has even more wide spread use when meaning our lovely microcontroller , so let's take this for the first, most important, meaning of the word Arduino !